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RSS2011 Vol. 23, No. 11
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2011,
23.
Abstract:
Male Babl/c mouses were exposed to 0.625 mW/cm2 and 1.25 mW/cm2 2856 MHz microwaves for 30 min×2 times. Venous blood samples were collected at 1 h,1 d,3 d，7 d,15 d and 30 d after exposure and differential counting of blood cells were performed． Immediate increases in white blood cell count and percentage, neutrophilic granulocyte count and percentage were observed after exposure to 0.625 mW/cm2 and 1.25 mW/cm2 microwave irradiations. On days 3，7 and 15，they elevated more significantly than contro1 group （p≤0.01）．Lymphocyte count and percentage decreased after exposure to both irradiations. On days 3，7 and 15， they reduced more significantly than contro1 grop （p≤0.01）. Both 0.625 mW/cm2 and 1.25 mW/cm2 dose exposures have little effect on， platelets and erythrocytes. Low dos
Male Babl/c mouses were exposed to 0.625 mW/cm2 and 1.25 mW/cm2 2856 MHz microwaves for 30 min×2 times. Venous blood samples were collected at 1 h,1 d,3 d，7 d,15 d and 30 d after exposure and differential counting of blood cells were performed． Immediate increases in white blood cell count and percentage, neutrophilic granulocyte count and percentage were observed after exposure to 0.625 mW/cm2 and 1.25 mW/cm2 microwave irradiations. On days 3，7 and 15，they elevated more significantly than contro1 group （p≤0.01）．Lymphocyte count and percentage decreased after exposure to both irradiations. On days 3，7 and 15， they reduced more significantly than contro1 grop （p≤0.01）. Both 0.625 mW/cm2 and 1.25 mW/cm2 dose exposures have little effect on， platelets and erythrocytes. Low dos
2011,
23.
Abstract:
The radiation generated in the process that the intense electron beam accelerator is running with pseudo load can lead to the black screen of the nearby computer and oscillograph. In this study, the research using experiment method is carried out on this problem. Three radiation periods are demonstrated in the experiment, corresponding to the time when the trigger signal arrives, the primary switch operates and the main switch operates, respectively. The radiation generated when the primary switch operates is larger than that generated when the main switch operates. The radiation in the second period reaches the largest intensity at the same height as the primary switch. The analysis of frequency spectra shows that the radiation in the experiment is mainly concentrated in low frequency ran
The radiation generated in the process that the intense electron beam accelerator is running with pseudo load can lead to the black screen of the nearby computer and oscillograph. In this study, the research using experiment method is carried out on this problem. Three radiation periods are demonstrated in the experiment, corresponding to the time when the trigger signal arrives, the primary switch operates and the main switch operates, respectively. The radiation generated when the primary switch operates is larger than that generated when the main switch operates. The radiation in the second period reaches the largest intensity at the same height as the primary switch. The analysis of frequency spectra shows that the radiation in the experiment is mainly concentrated in low frequency ran
2011,
23.
Abstract:
The paper analyzes the high voltage rectangle pulse generator with a Marx generator and a LC circuit in theory, and designs a pulse generator of this kind. The Marx generator is constituted of sixteen 100 kV, 400 nF capacitors, with a pre-triggered S-type circuit. The LC circuit is made by five capacitors the same as that of the Marx generator and a inductor of 1.5 H inductance. The simulation of Spice shows a 1.1 MV, 300 ns, rectangle pulse produced by this pulse generator. The middle stage of the Marx generator is used to trigger the LC circuit in order to synchronize this two parts.
The paper analyzes the high voltage rectangle pulse generator with a Marx generator and a LC circuit in theory, and designs a pulse generator of this kind. The Marx generator is constituted of sixteen 100 kV, 400 nF capacitors, with a pre-triggered S-type circuit. The LC circuit is made by five capacitors the same as that of the Marx generator and a inductor of 1.5 H inductance. The simulation of Spice shows a 1.1 MV, 300 ns, rectangle pulse produced by this pulse generator. The middle stage of the Marx generator is used to trigger the LC circuit in order to synchronize this two parts.
2011,
23: 1-5.
Abstract:
The proliferation changes of IAR20 and L-02 cells induced by 9.33 GHz high power pulse microwave(HPPM) have been investigated by MTT assay. The relations between HPPM parameters(pulse number, field intensity and pulse width) and cell proliferation are analyzed. The extent of proliferation decrease is recognized as the quantity of HPPM cell effects. The quantity of HPPM cell effects is in nonlinear exponential increase with the increase of pulse number when field intensity and pulse width remains fixed. The extent of proliferation decrease becomes greater with higher field intensity and longer pulse width, i.e. the quantity of HPPM cell effects is proportional to field intensity and pulse width. The difference of cell lines can influence the cell effects of HPPM with the same parameters, an
The proliferation changes of IAR20 and L-02 cells induced by 9.33 GHz high power pulse microwave(HPPM) have been investigated by MTT assay. The relations between HPPM parameters(pulse number, field intensity and pulse width) and cell proliferation are analyzed. The extent of proliferation decrease is recognized as the quantity of HPPM cell effects. The quantity of HPPM cell effects is in nonlinear exponential increase with the increase of pulse number when field intensity and pulse width remains fixed. The extent of proliferation decrease becomes greater with higher field intensity and longer pulse width, i.e. the quantity of HPPM cell effects is proportional to field intensity and pulse width. The difference of cell lines can influence the cell effects of HPPM with the same parameters, an
2011,
23: 2855- .
doi: 10.3788/HPLPB20112311.2855
Abstract:
With the analog to digital converter of three inverters, theoretical analysis and injection experiment of microwave effects are carried out on circuit unit level. The core chip of the circuit is 74HC04 or 74LVCU04A inverter. The latch process of the inverter is used to explain the nonlinear disturbance. The study is concentrated on the microwave effects on the circuit operating. Under the variation parameters of injected microwave pulse, such as amplitude, carrier frequency, and pulse width. At a fixed temperature, the threshold of effective injected microwave power for nonlinear disturbance of 10 % is 33 dBm for 74HC04 and 30 dBm for 74LVCU04A, when the carrier frequency of the injected microwave is below 3 GHz. The threshold increases with the increase of the carrier frequency. Additiona
With the analog to digital converter of three inverters, theoretical analysis and injection experiment of microwave effects are carried out on circuit unit level. The core chip of the circuit is 74HC04 or 74LVCU04A inverter. The latch process of the inverter is used to explain the nonlinear disturbance. The study is concentrated on the microwave effects on the circuit operating. Under the variation parameters of injected microwave pulse, such as amplitude, carrier frequency, and pulse width. At a fixed temperature, the threshold of effective injected microwave power for nonlinear disturbance of 10 % is 33 dBm for 74HC04 and 30 dBm for 74LVCU04A, when the carrier frequency of the injected microwave is below 3 GHz. The threshold increases with the increase of the carrier frequency. Additiona
2011,
23.
Abstract:
Our laboratory has developed a two-dimensional semiconductor device simulator to analyze the burnout mechanism of semiconductor devices with high power microwave injection. In this paper, the simulator is further developed to include the SPICE model of microstrip lines irradiated by an incident wave. The developed simulator can be used to analyze the high power microwave irradiation effects on PCB circuits with semiconductor devices. With the developed simulator, a practical PCB circuit including a low noise amplifier (LNA) is simulated in two cases, i. e. the PCB circuit is directly irradiated by an uniform plane wave and the PCB circuit is placed in a shielding cavity with a slot during irradiated. For the first case, different incident modes of plane wave are simulated and the burnout t
Our laboratory has developed a two-dimensional semiconductor device simulator to analyze the burnout mechanism of semiconductor devices with high power microwave injection. In this paper, the simulator is further developed to include the SPICE model of microstrip lines irradiated by an incident wave. The developed simulator can be used to analyze the high power microwave irradiation effects on PCB circuits with semiconductor devices. With the developed simulator, a practical PCB circuit including a low noise amplifier (LNA) is simulated in two cases, i. e. the PCB circuit is directly irradiated by an uniform plane wave and the PCB circuit is placed in a shielding cavity with a slot during irradiated. For the first case, different incident modes of plane wave are simulated and the burnout t
2011,
23.
Abstract:
Single-ended mixers were designed and made with ADS software. A set of mixers of different damage levels were then obtained after effects experiments of microwave injection. By measuring diode volt-ampere characteristics and analyzing failure mechanism, the paper establishes the damaged diode model through fitting. Based on this model, the equivalent circuit of damaged mixer is established. The simulation values of conversion loss are in accordance with the experiment ones. The model places a shunt resistance parallel connected with the junction resistance of normal diode, and the resistance is quite correlated with the damage level of the mixer. The smaller the resistance is, the more serious the damage is.
Single-ended mixers were designed and made with ADS software. A set of mixers of different damage levels were then obtained after effects experiments of microwave injection. By measuring diode volt-ampere characteristics and analyzing failure mechanism, the paper establishes the damaged diode model through fitting. Based on this model, the equivalent circuit of damaged mixer is established. The simulation values of conversion loss are in accordance with the experiment ones. The model places a shunt resistance parallel connected with the junction resistance of normal diode, and the resistance is quite correlated with the damage level of the mixer. The smaller the resistance is, the more serious the damage is.
2011,
23.
Abstract:
This paper studies low noise amplifier (LNA) failures under intentional electromagnetic environment (IEME) through SPICE simulation and direct injection experiment. The classic single-stage studied has strong gain suppression effects when superimposed with high-power microwave (HPM) pulse at input port. Both theoretical and experimental results obtained highlight that the SPICE model can be used to assess IEMI effects. The LNA gain-suppression duration will keep the maximum value when the injected microwave pulse width exceeds its threshold for fixed pulse power level. The duration can be well estimated by the RC constant of transistor base bias circuit. Finally, the mechanism of such LNA failure is discussed.
This paper studies low noise amplifier (LNA) failures under intentional electromagnetic environment (IEME) through SPICE simulation and direct injection experiment. The classic single-stage studied has strong gain suppression effects when superimposed with high-power microwave (HPM) pulse at input port. Both theoretical and experimental results obtained highlight that the SPICE model can be used to assess IEMI effects. The LNA gain-suppression duration will keep the maximum value when the injected microwave pulse width exceeds its threshold for fixed pulse power level. The duration can be well estimated by the RC constant of transistor base bias circuit. Finally, the mechanism of such LNA failure is discussed.
2011,
23.
Abstract:
The paper presents a high power bipolar pulse forming line based on Blumlein line and peaking-chopping(P-C) switch, and studies its operating principles. A high power bipolar pulse forming line is designed accordingly, and high voltage experiments about the pulse forming line are conducted on the 800 kV ultra-wideband high power pulse source. The effect of P-C switch and length of the pulse forming line on the output bipolar pulse is analyzed. The Blumlein bipolar pulse forming line can output bipolar pulses with peak voltages of -571.9 kV and +550.4 kV, and peak-to-peak interval of 740 ps, for the input pulse with 652.0 kV peak voltage and 2.1 ns width. The peak-peak voltage of the bipolar pulses is 1.72 times that of the input pulse, and the field-range product is 4.54 MV.
The paper presents a high power bipolar pulse forming line based on Blumlein line and peaking-chopping(P-C) switch, and studies its operating principles. A high power bipolar pulse forming line is designed accordingly, and high voltage experiments about the pulse forming line are conducted on the 800 kV ultra-wideband high power pulse source. The effect of P-C switch and length of the pulse forming line on the output bipolar pulse is analyzed. The Blumlein bipolar pulse forming line can output bipolar pulses with peak voltages of -571.9 kV and +550.4 kV, and peak-to-peak interval of 740 ps, for the input pulse with 652.0 kV peak voltage and 2.1 ns width. The peak-peak voltage of the bipolar pulses is 1.72 times that of the input pulse, and the field-range product is 4.54 MV.
2011,
23.
Abstract:
A kind of coaxial capacitor with low-inductance, high-current conducting ability and long-life is investigated. Considering its voltage, inductance, ability of conducting current and connecting manner with switch, the paper theoretically determines the structure of its component, insulator and electrode. Then with elaborately designed circuits of experiment, the voltage, inductance, ability of conducting current and lifetime of the capacitor are tested. The results indicate that the capacitance of the capacitor is 1.5 μF, the rated voltage is 100 kV, the rated current is 250 kA, the peak current is higher than 300 kA, the inductance is less than 20 nH, the energy density is 205 J/L, and the lifetime exceeds 6 000 shots.
A kind of coaxial capacitor with low-inductance, high-current conducting ability and long-life is investigated. Considering its voltage, inductance, ability of conducting current and connecting manner with switch, the paper theoretically determines the structure of its component, insulator and electrode. Then with elaborately designed circuits of experiment, the voltage, inductance, ability of conducting current and lifetime of the capacitor are tested. The results indicate that the capacitance of the capacitor is 1.5 μF, the rated voltage is 100 kV, the rated current is 250 kA, the peak current is higher than 300 kA, the inductance is less than 20 nH, the energy density is 205 J/L, and the lifetime exceeds 6 000 shots.
2011,
23.
Abstract:
The primary objective of this article is to research the effect of pulsed discharge spark resistance on output pulse front edge of gas spark switch. The analysis on characteristics of spark discharge resistance is an important foundation to study switching energy loss, arc thermal plasma physical state, and repetitive switch insulation recovery characteristics, etc. Combined with the gas spark switch circuit model established, switch inductance and resistance have been taken into account to analyze the impact on the pulse front edge. For the high voltage gas switch with large gap, spark resistance is the dominating factor affecting the front edge of output pulse.
The primary objective of this article is to research the effect of pulsed discharge spark resistance on output pulse front edge of gas spark switch. The analysis on characteristics of spark discharge resistance is an important foundation to study switching energy loss, arc thermal plasma physical state, and repetitive switch insulation recovery characteristics, etc. Combined with the gas spark switch circuit model established, switch inductance and resistance have been taken into account to analyze the impact on the pulse front edge. For the high voltage gas switch with large gap, spark resistance is the dominating factor affecting the front edge of output pulse.
2011,
23.
Abstract:
Two kinds of convolution methods were designed to optimize the output characteristics of rolled strip pulse forming line(RSPFL). Simulation results show that convolution methods influence the electromagnetic field distribution in the RSPFL, especially the coupling characteristics between conductors. Along with the tranditional convolution method, three kinds of RSPFLs were made accordingly. The results show that different convolution methods do affect the waveform on the load when the time-lapse is 100 ns, impedance is 1.1 Ω, and charge voltage is 25 kV. The two-plate structure has similar output characteristics with the tranditional three-plate one. The simulation results agree with the experimental ones very well. Thus a suitable convolution method could improve the output characteristi
Two kinds of convolution methods were designed to optimize the output characteristics of rolled strip pulse forming line(RSPFL). Simulation results show that convolution methods influence the electromagnetic field distribution in the RSPFL, especially the coupling characteristics between conductors. Along with the tranditional convolution method, three kinds of RSPFLs were made accordingly. The results show that different convolution methods do affect the waveform on the load when the time-lapse is 100 ns, impedance is 1.1 Ω, and charge voltage is 25 kV. The two-plate structure has similar output characteristics with the tranditional three-plate one. The simulation results agree with the experimental ones very well. Thus a suitable convolution method could improve the output characteristi
2011,
23.
Abstract:
In order to solve the electromagnetic interference among multi-loaded lines in series when the Tesla-PFN(pulse forming network) long pulse power generator operates under high voltage, the structure of the annular loaded lines in series is optimized and designed, with emphases on the impedance matching between loaded lines and pulse forming line(PFL) and the high voltage insulation of loaded lines. The structure of transition part is optimized, which realizes good impedance matching between loaded lines and PFL and makes the top of the output pulse flat. The electric field distribution of the PFNs is calculated by using a static electric field analysis software, and the distribution is evened by adjusting the shape and location of shielding loop.
In order to solve the electromagnetic interference among multi-loaded lines in series when the Tesla-PFN(pulse forming network) long pulse power generator operates under high voltage, the structure of the annular loaded lines in series is optimized and designed, with emphases on the impedance matching between loaded lines and pulse forming line(PFL) and the high voltage insulation of loaded lines. The structure of transition part is optimized, which realizes good impedance matching between loaded lines and PFL and makes the top of the output pulse flat. The electric field distribution of the PFNs is calculated by using a static electric field analysis software, and the distribution is evened by adjusting the shape and location of shielding loop.
2011,
23.
Abstract:
One double-channel output structure of spiral PFL(pulse forming line) with an outer shield and an inner cylinder is presented. This kind of spiral PFL comprises a high-coupling Tesla transformer with built-in ferromagnetic material as the inner and the outer cylinders. When the secondary channel outputs pulses in a matched way, the flat-topped fluctuation of the main pulse will be removed, and most of the stored energy will be delivered to the main load. The problem of the spiral line put forward by Korovin can thus be resolved. The comparison of two technical methods, the double-channel spiral-PFL one and the one applied in SINUS-700/130, shows that the flatness of the output pulse for the former is better and the output power increases by 29%, whereas the secondary load will consume 11%
One double-channel output structure of spiral PFL(pulse forming line) with an outer shield and an inner cylinder is presented. This kind of spiral PFL comprises a high-coupling Tesla transformer with built-in ferromagnetic material as the inner and the outer cylinders. When the secondary channel outputs pulses in a matched way, the flat-topped fluctuation of the main pulse will be removed, and most of the stored energy will be delivered to the main load. The problem of the spiral line put forward by Korovin can thus be resolved. The comparison of two technical methods, the double-channel spiral-PFL one and the one applied in SINUS-700/130, shows that the flatness of the output pulse for the former is better and the output power increases by 29%, whereas the secondary load will consume 11%
2011,
23.
Abstract:
The solid-state pulsed power device is a new development trend of pulsed power technology. This paper reports the development of the solid-state pulse forming line(PFL) in Institute of Fluid Physics, China Academy of Engineering Physics. The experimental results of the ferroelectric ceramic PFL and glass-ceramic PFL are shown. The output pulse properties of the ferroelectric ceramic PFL and glass-ceramic PFL are analyzed.
The solid-state pulsed power device is a new development trend of pulsed power technology. This paper reports the development of the solid-state pulse forming line(PFL) in Institute of Fluid Physics, China Academy of Engineering Physics. The experimental results of the ferroelectric ceramic PFL and glass-ceramic PFL are shown. The output pulse properties of the ferroelectric ceramic PFL and glass-ceramic PFL are analyzed.
2011,
23.
Abstract:
Two kinds of Photoconductive semiconductor switch(PCSSs) with bulk structure are studied experimentally, which are fabricated from semi-insulating GaAs. The first switch has a size of 10 mm×10 mm×0.6 mm, whose electrodes are 6 mm in diameter on the opposite side of the chip. The second one has a size of 15 mm×15 mm×3 mm, whose electrodes are 8 mm in diameter on the opposite side of the chip. The withstand voltage of the first switch is tested under pulse voltages with different full-width-at-half-maximum. A maximum withstand voltage of 7.6 kV is achieved, which means the breakdown electric field is 127 kV/cm. The volt-ampere performance at DC bias voltage and dark condition of the second switch is tested as well as its triggered performance. The maximum current of the switch is more th
Two kinds of Photoconductive semiconductor switch(PCSSs) with bulk structure are studied experimentally, which are fabricated from semi-insulating GaAs. The first switch has a size of 10 mm×10 mm×0.6 mm, whose electrodes are 6 mm in diameter on the opposite side of the chip. The second one has a size of 15 mm×15 mm×3 mm, whose electrodes are 8 mm in diameter on the opposite side of the chip. The withstand voltage of the first switch is tested under pulse voltages with different full-width-at-half-maximum. A maximum withstand voltage of 7.6 kV is achieved, which means the breakdown electric field is 127 kV/cm. The volt-ampere performance at DC bias voltage and dark condition of the second switch is tested as well as its triggered performance. The maximum current of the switch is more th
2011,
23.
Abstract:
This paper proposes a series resonant converter based on HF (high-frequency) AC-link technology, and gives the analysis of its working principle and working process, as well as the control method and system block diagram. Simulation and experiment ware carried out, and the experimental results show that the converter can make the grid-side voltage and current in the same phase, and the grid-side current harmonic level is low. Besides, series resonance has high efficiency and constant-current charging characteristics. Thus, the converter has high power factor, high efficiency and low harmonic.
This paper proposes a series resonant converter based on HF (high-frequency) AC-link technology, and gives the analysis of its working principle and working process, as well as the control method and system block diagram. Simulation and experiment ware carried out, and the experimental results show that the converter can make the grid-side voltage and current in the same phase, and the grid-side current harmonic level is low. Besides, series resonance has high efficiency and constant-current charging characteristics. Thus, the converter has high power factor, high efficiency and low harmonic.
2011,
23.
Abstract:
The design goals of a 20 GW/100 Hz repetitive pulsed accelerator are: output power exceeding 20 GW, pulse width about 40 ns, and repetition rate ranging from 1 to 100 Hz. General design of the device based on Tesla technology is described in this paper. For charging the forming line, a Tesla transformer with open magnetic core is used, whose efficiency exceeds 75% by optimization. The output power of the device reaches 22.6 GW at 100 Hz repetition rate, and operation experiments have verified reliability. The device is was mainly applied to generating intense current. It can also be applied to mechanism researches of the intense current diode and high power microwave.
The design goals of a 20 GW/100 Hz repetitive pulsed accelerator are: output power exceeding 20 GW, pulse width about 40 ns, and repetition rate ranging from 1 to 100 Hz. General design of the device based on Tesla technology is described in this paper. For charging the forming line, a Tesla transformer with open magnetic core is used, whose efficiency exceeds 75% by optimization. The output power of the device reaches 22.6 GW at 100 Hz repetition rate, and operation experiments have verified reliability. The device is was mainly applied to generating intense current. It can also be applied to mechanism researches of the intense current diode and high power microwave.
2011,
23.
Abstract:
A compact wideband impulse radiating generator directly driven by a fast rise-time Marx generator is designed. Low-inductance capacitors of 3 300 pF are chosen as energy storage capacitors, and helix inductors are utilized as charging and grounding elements. By means of rapid discharge of each short gas spark gap, wave erection can be realized on the output load. The Marx generator is fitted into a 477 mm long tube with 145 mm diameter. The generator is pressurized with an N2/SF6 mixture. The system consists of two parts, wave oscillator and radiating antenna, and can work at 10 Hz repetition rate. The peak radiated field is about 40 kV/m at 1 m from the radiating antenna, with a center frequency of 206 MHz.
A compact wideband impulse radiating generator directly driven by a fast rise-time Marx generator is designed. Low-inductance capacitors of 3 300 pF are chosen as energy storage capacitors, and helix inductors are utilized as charging and grounding elements. By means of rapid discharge of each short gas spark gap, wave erection can be realized on the output load. The Marx generator is fitted into a 477 mm long tube with 145 mm diameter. The generator is pressurized with an N2/SF6 mixture. The system consists of two parts, wave oscillator and radiating antenna, and can work at 10 Hz repetition rate. The peak radiated field is about 40 kV/m at 1 m from the radiating antenna, with a center frequency of 206 MHz.
2011,
23.
Abstract:
The paper presents the principle of the charging technology for nanosecond transmission line, and designs an experimental setup for high power ultra-wideband pulse generation accordingly. The working process of the experimental setup is studied by simulation. The output waveforms, output power and operation stability are debugged during experiment. The pulse power, full width, repetitive frequency are respectively 30 GW, 1.6 ns, 100 Hz on a 2.7 Ω pulse transmission line in the experiment on a 1.2 MV pulse source. The experimental setup operates stably with results satisfying the design requirements.
The paper presents the principle of the charging technology for nanosecond transmission line, and designs an experimental setup for high power ultra-wideband pulse generation accordingly. The working process of the experimental setup is studied by simulation. The output waveforms, output power and operation stability are debugged during experiment. The pulse power, full width, repetitive frequency are respectively 30 GW, 1.6 ns, 100 Hz on a 2.7 Ω pulse transmission line in the experiment on a 1.2 MV pulse source. The experimental setup operates stably with results satisfying the design requirements.
2011,
23.
Abstract:
The theoretical analysis shows that the interlayer voltage of magnetic core is directly proportional to the tape thickness and width along with the working voltage of magnetic core, while inversely proportional to the effective cross-sectional area of magnetic core. The experiments show that the oxide film naturally formed in processing of magnetic core can withstand voltage of 3.0 to 3.6 V. If the interlayer voltage exceeds the withstand voltage, an inflection point will appear on the load waveform and thus the flux swing will fail to reach the design value. In practical situations, reducing the tape width and keeping the interlayer voltage under 3 V can improve the working voltage and make fuller use of the flux swing.
The theoretical analysis shows that the interlayer voltage of magnetic core is directly proportional to the tape thickness and width along with the working voltage of magnetic core, while inversely proportional to the effective cross-sectional area of magnetic core. The experiments show that the oxide film naturally formed in processing of magnetic core can withstand voltage of 3.0 to 3.6 V. If the interlayer voltage exceeds the withstand voltage, an inflection point will appear on the load waveform and thus the flux swing will fail to reach the design value. In practical situations, reducing the tape width and keeping the interlayer voltage under 3 V can improve the working voltage and make fuller use of the flux swing.
2011,
23.
Abstract:
A pulse-forming line with three conductor coaxial-line and Tesla transformer is presented. The electric field distribution between inner and outer conductors is improved and the average field intensity is increased by using the middle conductor, thus higher peak voltage and energy storage of the pulse-forming line is obtained. The pulse-forming line is charged by Tesla transformer with dual secondary windings. The characteristics of circuit and the voltage waveforms of the secondary windings are analyzed. The charge time when the voltage ratio of the two conductor gaps reaches its optimal value is also presented. The voltage and energy storage curves of the pulse-forming line are obtained through optimizing radiuses of the inner and middle conductors. The result shows that both the voltage
A pulse-forming line with three conductor coaxial-line and Tesla transformer is presented. The electric field distribution between inner and outer conductors is improved and the average field intensity is increased by using the middle conductor, thus higher peak voltage and energy storage of the pulse-forming line is obtained. The pulse-forming line is charged by Tesla transformer with dual secondary windings. The characteristics of circuit and the voltage waveforms of the secondary windings are analyzed. The charge time when the voltage ratio of the two conductor gaps reaches its optimal value is also presented. The voltage and energy storage curves of the pulse-forming line are obtained through optimizing radiuses of the inner and middle conductors. The result shows that both the voltage
2011,
23.
Abstract:
A wideband radiation system with tunable center frequency is presented. The system is composed of a pulsed power source, a λ/4 coaxial transmission line oscillator, a ring switch, a coupler and a radiation antenna. The resonant frequency of the oscillator can be modified by sliding the ring switch on the inner transmission line. The coupler is designed with lumped capacitance and distributed inductance. The combined electric and magnetic dipoles antenna is designed in the range of 200 MHz to 400 MHz. And the wideband system is charged with a Tesla transformer whose output voltage is 500 kV on the 200 pF secondary capacitor. The range-normalized radiated E-field radiation factor is in the range of 95 kV to 130 kV and the FWHM of frequency spectrum is in the range of 10% to 30%.
A wideband radiation system with tunable center frequency is presented. The system is composed of a pulsed power source, a λ/4 coaxial transmission line oscillator, a ring switch, a coupler and a radiation antenna. The resonant frequency of the oscillator can be modified by sliding the ring switch on the inner transmission line. The coupler is designed with lumped capacitance and distributed inductance. The combined electric and magnetic dipoles antenna is designed in the range of 200 MHz to 400 MHz. And the wideband system is charged with a Tesla transformer whose output voltage is 500 kV on the 200 pF secondary capacitor. The range-normalized radiated E-field radiation factor is in the range of 95 kV to 130 kV and the FWHM of frequency spectrum is in the range of 10% to 30%.
2011,
23.
Abstract:
The paper designs a high power ultra-wideband(UWB) radiation source, which consists of high voltage pulsed power supply, pulse forming line, impedance transformation unit, transmission line, etc. The parameters of all the parts are analyzed and matched. And an experimental set is built accordingly. An over 30 GW pulse with duration of 1.6 ns can be obtained on the 2.7 Ω pulse forming line. Through Cassegrain dual reflector antenna, the effective isotropic radiated power exceeds 2×1012 W, the radiated field factor exceeds 8 MV, and the 3 dB widths of power of E- and H-plane of radiation are 2.35° and 2.27°, respectively.
The paper designs a high power ultra-wideband(UWB) radiation source, which consists of high voltage pulsed power supply, pulse forming line, impedance transformation unit, transmission line, etc. The parameters of all the parts are analyzed and matched. And an experimental set is built accordingly. An over 30 GW pulse with duration of 1.6 ns can be obtained on the 2.7 Ω pulse forming line. Through Cassegrain dual reflector antenna, the effective isotropic radiated power exceeds 2×1012 W, the radiated field factor exceeds 8 MV, and the 3 dB widths of power of E- and H-plane of radiation are 2.35° and 2.27°, respectively.
2011,
23.
Abstract:
The paper analyzes the reason why the pulse top spreads and the rise time shortens in a fault experiment on long pulse high power linear transformer microwave driver. Effects of waves superposition delay are discussed based on current transmission model. Output pulse waveforms are then derived by three dimensional simulation on the experimental prototype under excitations of different time sequences. The result suggests that, if the module closest to the diode is the first module physically, the delay from the switch triggered can be offsetted by waves superposition delay, and thus the wave optimization can be realized.
The paper analyzes the reason why the pulse top spreads and the rise time shortens in a fault experiment on long pulse high power linear transformer microwave driver. Effects of waves superposition delay are discussed based on current transmission model. Output pulse waveforms are then derived by three dimensional simulation on the experimental prototype under excitations of different time sequences. The result suggests that, if the module closest to the diode is the first module physically, the delay from the switch triggered can be offsetted by waves superposition delay, and thus the wave optimization can be realized.
2011,
23.
Abstract:
This paper presents a long-pulse modulator based on parallel resonant waveform superposition technique, which uses multiple modules (in parallel) for waveform superposition to reduce rising edge while keep a certain voltage ripple and increase the output power, with each module using a parallel resonant structure. In order to stabilize the output voltage, and to minimize switching losses, the frequency and phase combined control method is applied. Its principle, feedforward voltage control principle and design of resonant parameters are described. The simulation of three modules in parallel shows that, with the input DC voltage varying within 450 to 550 V, the structure under forward control at 50 kHz resonant frequency generates 60 kV voltage on the 5.2 kΩ load resistor, whose rising ti
This paper presents a long-pulse modulator based on parallel resonant waveform superposition technique, which uses multiple modules (in parallel) for waveform superposition to reduce rising edge while keep a certain voltage ripple and increase the output power, with each module using a parallel resonant structure. In order to stabilize the output voltage, and to minimize switching losses, the frequency and phase combined control method is applied. Its principle, feedforward voltage control principle and design of resonant parameters are described. The simulation of three modules in parallel shows that, with the input DC voltage varying within 450 to 550 V, the structure under forward control at 50 kHz resonant frequency generates 60 kV voltage on the 5.2 kΩ load resistor, whose rising ti
2011,
23.
Abstract:
Effects of impedance discontinuity in magnetically insulated transmission line(MITL) region and diode time-dependent impedance on diode wave process have been studied through theoretical analysis. If the time delay of the transmission lines in MITL region is much shorter than the pulse width of the incident wave, the amplitudes of cathode voltage and current can be represented by those measured in the anterior part of the diode and the ratio of voltage and current is diode impedance. To steepen the leading edge of cathode voltage and current, the impedance of the transmission lines in MITL region is suggested to increase along the direction of the incident wave and should be the root-mean-square of the effective impedances on both ends. The leading edge of measured voltage and current can
Effects of impedance discontinuity in magnetically insulated transmission line(MITL) region and diode time-dependent impedance on diode wave process have been studied through theoretical analysis. If the time delay of the transmission lines in MITL region is much shorter than the pulse width of the incident wave, the amplitudes of cathode voltage and current can be represented by those measured in the anterior part of the diode and the ratio of voltage and current is diode impedance. To steepen the leading edge of cathode voltage and current, the impedance of the transmission lines in MITL region is suggested to increase along the direction of the incident wave and should be the root-mean-square of the effective impedances on both ends. The leading edge of measured voltage and current can
2011,
23.
Abstract:
The electrohydrodynamic equation of bubble deformation in liquid was derived based on the ellipsoid model of bubble breakdown in liquid. With the software Comsol being used to track the bubble deformation, the impact of air bubble deformation in dielectric liquid under strong electric field was discussed. The results show that the spherical bubbles turn into elliptical ones with the combined action of electric stress and surface tension. In order to avoid bubble breakdown, applying pressure is a practical measure. Moreover, the applied pressure and the bubble aspect ratio are in direct proportion to electric field strength and original bubble radius.
The electrohydrodynamic equation of bubble deformation in liquid was derived based on the ellipsoid model of bubble breakdown in liquid. With the software Comsol being used to track the bubble deformation, the impact of air bubble deformation in dielectric liquid under strong electric field was discussed. The results show that the spherical bubbles turn into elliptical ones with the combined action of electric stress and surface tension. In order to avoid bubble breakdown, applying pressure is a practical measure. Moreover, the applied pressure and the bubble aspect ratio are in direct proportion to electric field strength and original bubble radius.
2011,
23.
Abstract:
Experimental research on synchronized operation of 4 parallel-connected 1 GW nanosecond pulse generators is presented. With trigatron as trigger switch, the synchronized operation is successfully achieved. The jitter time of trigation is 0.2 ns. The mutual spread of four 6 ns wide pulses is lower than 1 ns (probability above 95%) with an average value of 630 ps at a peak power of 1 GW (230 kV on 50 Ω load) of each parallel-connected module.
Experimental research on synchronized operation of 4 parallel-connected 1 GW nanosecond pulse generators is presented. With trigatron as trigger switch, the synchronized operation is successfully achieved. The jitter time of trigation is 0.2 ns. The mutual spread of four 6 ns wide pulses is lower than 1 ns (probability above 95%) with an average value of 630 ps at a peak power of 1 GW (230 kV on 50 Ω load) of each parallel-connected module.
2011,
23.
Abstract:
This paper presented the particle-in-cell simulations on the expansion process of the plasma with a density about 1014 cm-3 near the cathode surface. The plasma expanding with velocity about 1 cm/μs was observed. The expansion process was analyzed based on the observations of the particle distributions, the particle velocity and the axial electric field at different time. The influences of the plasma temperature and plasma formation rate on the plasma expansion process were discussed. It is shown that the appearance of ions strengthens the electric field on the cathode surface, leading to the increase of electron beam density. The electron field at the plasma front decreases with the increase of beam density, thus the movement of ions towards anode can be realized. The plasma expansion ve
This paper presented the particle-in-cell simulations on the expansion process of the plasma with a density about 1014 cm-3 near the cathode surface. The plasma expanding with velocity about 1 cm/μs was observed. The expansion process was analyzed based on the observations of the particle distributions, the particle velocity and the axial electric field at different time. The influences of the plasma temperature and plasma formation rate on the plasma expansion process were discussed. It is shown that the appearance of ions strengthens the electric field on the cathode surface, leading to the increase of electron beam density. The electron field at the plasma front decreases with the increase of beam density, thus the movement of ions towards anode can be realized. The plasma expansion ve
2011,
23.
Abstract:
A tri-electrode self-steepening switch was researched. Then a triggering system was designed with a transformer driver and the self-steepening switch to satisfy the requirements of the trigatron. Statistical analysis on steepening parameters of the switch was conducted under multiple driving modes to reach the optimized self-steepening mode. The optimization combination of switching polarity, working electric field, UV radiation intensity and time were determined. The switching possibility of the trigatron was obviously improved when the self-steepening segment was inserted. Meanwhile, the delay and the jitter of the trigatron decreased significantly, and its working voltage-ratio range was broadened.
A tri-electrode self-steepening switch was researched. Then a triggering system was designed with a transformer driver and the self-steepening switch to satisfy the requirements of the trigatron. Statistical analysis on steepening parameters of the switch was conducted under multiple driving modes to reach the optimized self-steepening mode. The optimization combination of switching polarity, working electric field, UV radiation intensity and time were determined. The switching possibility of the trigatron was obviously improved when the self-steepening segment was inserted. Meanwhile, the delay and the jitter of the trigatron decreased significantly, and its working voltage-ratio range was broadened.
2011,
23.
Abstract:
Taking a Tesla transformer as a pulsed power source, the insulation recovery characteristics of a 4 mm-gap length, 4 MPa-pressure N2 switch are researched with two-pulse method. The material of the switch is copper and the shape is circular. The results indicate that, the switch is almost conducting within about 0.3 ms after the end of discharge, which belongs to the deionization stage; then the insulation recovery factor rises up exponentially until the switch recovers completely at about 3 ms, which belongs to the gas temperature recovering stage. The Tesla transformer makes the sectional characteristic of the insulation recovery curve of the high-voltage N2 spark switch more obvious. The reason may be that the resistance of the spark channels is paralleled with the secondary capacitance
Taking a Tesla transformer as a pulsed power source, the insulation recovery characteristics of a 4 mm-gap length, 4 MPa-pressure N2 switch are researched with two-pulse method. The material of the switch is copper and the shape is circular. The results indicate that, the switch is almost conducting within about 0.3 ms after the end of discharge, which belongs to the deionization stage; then the insulation recovery factor rises up exponentially until the switch recovers completely at about 3 ms, which belongs to the gas temperature recovering stage. The Tesla transformer makes the sectional characteristic of the insulation recovery curve of the high-voltage N2 spark switch more obvious. The reason may be that the resistance of the spark channels is paralleled with the secondary capacitance
2011,
23.
Abstract:
The paper studies the higher order parasitic mode oscillation in input cavity and idler cavity of relativistic klystron amplifier(RKA). The parasitic mode in resonant cavity is proved to be TM11 mode, which is transformed into TE11 mode in drift tube. According to the transporting property of the parasitic mode in drift tube, the microwave attenuating material placed in the inner wall of drift tube is adopted to suppress the parasitic mode oscillation. The suppression of parasitic mode growth is also analyzed with microwave attenuating material of different conductivity and length. The three dimensional simulation of an RKA with attenuating material is carried out, and the results show that the introduction of proper microwave attenuating material can well suppress parasitic mode oscillati
The paper studies the higher order parasitic mode oscillation in input cavity and idler cavity of relativistic klystron amplifier(RKA). The parasitic mode in resonant cavity is proved to be TM11 mode, which is transformed into TE11 mode in drift tube. According to the transporting property of the parasitic mode in drift tube, the microwave attenuating material placed in the inner wall of drift tube is adopted to suppress the parasitic mode oscillation. The suppression of parasitic mode growth is also analyzed with microwave attenuating material of different conductivity and length. The three dimensional simulation of an RKA with attenuating material is carried out, and the results show that the introduction of proper microwave attenuating material can well suppress parasitic mode oscillati
2011,
23.
Abstract:
Based on Open object libraries, an open-source library for computer aided geometry design (CAGD), the technique of complex geometry modeling and conformal grid generation used for fully electromagnetic particle simulation is given. The characteristics of Open CASCADE are introduced, the design, pattern and capability of EasyEMModeling, our self-developed codes for complex geometry modeling, are introduced, and the generation method of conformal boundary in Yee grids is given by using line-surface intersection function offered by Open CASCADE. Finally, the technique is verified by a 3D numerical experiment.
Based on Open object libraries, an open-source library for computer aided geometry design (CAGD), the technique of complex geometry modeling and conformal grid generation used for fully electromagnetic particle simulation is given. The characteristics of Open CASCADE are introduced, the design, pattern and capability of EasyEMModeling, our self-developed codes for complex geometry modeling, are introduced, and the generation method of conformal boundary in Yee grids is given by using line-surface intersection function offered by Open CASCADE. Finally, the technique is verified by a 3D numerical experiment.
2011,
23.
Abstract:
NEPTUNE is a three-dimensional fully parallel electromagnetic code to solve electromagnetic problem in high power microwave(HPM) devices with complex geometry. This paper introduces the following three parallelization methods used in the code. For massively computation, the “block-patch” two level parallel domain decomposition strategy is provided to scale the computation size to thousands of processor cores. Based on the geometry information, the mesh is reconfigured using the adaptive technology to get rid of invalid grid cells, and thus the storage amount and parallel execution time decrease sharply. On the basis of traditional Boris’ successive over relaxation (SOR) iteration method, a parallel Poisson solver on irregular domains is provided with red and black ordering technology an
NEPTUNE is a three-dimensional fully parallel electromagnetic code to solve electromagnetic problem in high power microwave(HPM) devices with complex geometry. This paper introduces the following three parallelization methods used in the code. For massively computation, the “block-patch” two level parallel domain decomposition strategy is provided to scale the computation size to thousands of processor cores. Based on the geometry information, the mesh is reconfigured using the adaptive technology to get rid of invalid grid cells, and thus the storage amount and parallel execution time decrease sharply. On the basis of traditional Boris’ successive over relaxation (SOR) iteration method, a parallel Poisson solver on irregular domains is provided with red and black ordering technology an
2011,
23.
Abstract:
In this article, the parallel performance test of JEMS- FDTD on MPP(Massively Parallel Processor) is introduced, including the performance of different patch size, single- node and multi- node MPI/OPENMP hybrid parallel performance, and large scale parallel performance. The test shows that JEMS- FDTD is capable of performing parallel computation on tens of thousands processor cores efficiently. The computation and analyzing of a computer case with complex structure illuminated by pulsed electromagnetic wave is introduced an example, which demonstrates JEMS- FDTD’s capability of solving electric- large- scale electromagnetic propagation, radiation, coupling problems on MPP with high efficiency.
In this article, the parallel performance test of JEMS- FDTD on MPP(Massively Parallel Processor) is introduced, including the performance of different patch size, single- node and multi- node MPI/OPENMP hybrid parallel performance, and large scale parallel performance. The test shows that JEMS- FDTD is capable of performing parallel computation on tens of thousands processor cores efficiently. The computation and analyzing of a computer case with complex structure illuminated by pulsed electromagnetic wave is introduced an example, which demonstrates JEMS- FDTD’s capability of solving electric- large- scale electromagnetic propagation, radiation, coupling problems on MPP with high efficiency.
2011,
23.
Abstract:
According to the structural and feeding characteristics of beam waveguide system, the physical model for the excitation, transmission and radiation problems in beam waveguide with arbitrary shape is set up by using the volume-surface integral equation. The matching state at the feeding area is described accurately by the mode matching method. The solutions of electric field distribution and the aperture radiation field of beam waveguide are given by using the multilevel fast multipole algorithm (MLFMA), which is a numerical algorithm with high efficiency. The example demonstrates that the method proposed can provide steady and accurate numerical solutions for the excitation-transmission-radiation problems in beam waveguide with arbitrary shape and electrically large size.
According to the structural and feeding characteristics of beam waveguide system, the physical model for the excitation, transmission and radiation problems in beam waveguide with arbitrary shape is set up by using the volume-surface integral equation. The matching state at the feeding area is described accurately by the mode matching method. The solutions of electric field distribution and the aperture radiation field of beam waveguide are given by using the multilevel fast multipole algorithm (MLFMA), which is a numerical algorithm with high efficiency. The example demonstrates that the method proposed can provide steady and accurate numerical solutions for the excitation-transmission-radiation problems in beam waveguide with arbitrary shape and electrically large size.
2011,
23.
Abstract:
This paper researches the high frequency characteristics of coaxial boundary-loaded resonator with three cavities.It adopts the Borgnis potential function in cylindrical coordinate system to solve the field expression in each region, and then uses boundary conditions and matching conditions in adjacent domains to derive the dispersion relation and field expression of the angularly uniform TM mode in the resonator. The resonant frequency and field distribution obtained are basically consistent with the simulation results.
This paper researches the high frequency characteristics of coaxial boundary-loaded resonator with three cavities.It adopts the Borgnis potential function in cylindrical coordinate system to solve the field expression in each region, and then uses boundary conditions and matching conditions in adjacent domains to derive the dispersion relation and field expression of the angularly uniform TM mode in the resonator. The resonant frequency and field distribution obtained are basically consistent with the simulation results.
2011,
23.
Abstract:
This paper studies the method of source stirring, especially using multiple sources to improve the field uniformity in reverberation chambers (RCs). Firstly, the factors that may affect the field distribution in RCs are summarized, according to the Maxwell’s equations in ideal rectangular resonators. Then the focus is on the effects of multiple sources on the electromagnetic field distributions in RCs, including the maximum and the standard deviation of electric field strength and the isotropy as well. The results show that multiple sources can improve the field uniformity effectively and are useful in constructing a homogenous electromagnetic field environment for high-power microwave effect test on subsystems.
This paper studies the method of source stirring, especially using multiple sources to improve the field uniformity in reverberation chambers (RCs). Firstly, the factors that may affect the field distribution in RCs are summarized, according to the Maxwell’s equations in ideal rectangular resonators. Then the focus is on the effects of multiple sources on the electromagnetic field distributions in RCs, including the maximum and the standard deviation of electric field strength and the isotropy as well. The results show that multiple sources can improve the field uniformity effectively and are useful in constructing a homogenous electromagnetic field environment for high-power microwave effect test on subsystems.
2011,
23.
Abstract:
The paper describes the explosion electron emission resulted from microwave radiation field in microwave tube, including the analysis of alternating field-emission and the temperature distribution on the whisker. The deduced equation provides the heating speed of the whisker, besides the relation of produced plasma intensity with amplitude of microwave, electric conductivity, thermal conductivity, mass density and specific heat capacity. When the time is much longer than the period of microwave, the whisker temperature increases linearly with time. The rise ratio of the temperature can reach 3.22×1010 ℃/s, and the whisker may gasify and form plasma in a timescale of hundred nanoseconds.
The paper describes the explosion electron emission resulted from microwave radiation field in microwave tube, including the analysis of alternating field-emission and the temperature distribution on the whisker. The deduced equation provides the heating speed of the whisker, besides the relation of produced plasma intensity with amplitude of microwave, electric conductivity, thermal conductivity, mass density and specific heat capacity. When the time is much longer than the period of microwave, the whisker temperature increases linearly with time. The rise ratio of the temperature can reach 3.22×1010 ℃/s, and the whisker may gasify and form plasma in a timescale of hundred nanoseconds.
2011,
23.
Abstract:
A high power passive limiter based on PIN diode is presented. The main factors affecting its performance, such as power capability, limiting levels, peak leaking, response time, and recovery time, are presented. A passive PIN limiter using Schottky detection and an active limiter are realized based on microstrip line. The simulated results indicate that the threshold level and the limiting level of the passive limiter are about -3 dBm and 15 dBm, respectively, and it can withstand peak pulses of about 60 dBm. A high power measurement platform is established to measure the performance of the designed limiters. High isolation between high power signal and small signal is obtained using dual-band dual-path coupling method so that periodic pulsed and continuous wave high power measurement can
A high power passive limiter based on PIN diode is presented. The main factors affecting its performance, such as power capability, limiting levels, peak leaking, response time, and recovery time, are presented. A passive PIN limiter using Schottky detection and an active limiter are realized based on microstrip line. The simulated results indicate that the threshold level and the limiting level of the passive limiter are about -3 dBm and 15 dBm, respectively, and it can withstand peak pulses of about 60 dBm. A high power measurement platform is established to measure the performance of the designed limiters. High isolation between high power signal and small signal is obtained using dual-band dual-path coupling method so that periodic pulsed and continuous wave high power measurement can
2011,
23.
Abstract:
The paper studies the structure, electron beam parameters and beam-wave interaction of a complex cavity with gradual transition employed in the 94 GHz gyrotron. A self-consistent field nonlinear theoretical analysis is used and numerical simulation results for electron beam interaction with the modep air H61-H62 are given. A pulse output power of 78 kW is obtained for the gyrotron by simulation at the beam voltage of 40 kV with beam current of 10 A, velocity ratio of 1.3, and magnetic field of 3.6 T, corresponding to a beam-wave interaction efficiency of 39%.
The paper studies the structure, electron beam parameters and beam-wave interaction of a complex cavity with gradual transition employed in the 94 GHz gyrotron. A self-consistent field nonlinear theoretical analysis is used and numerical simulation results for electron beam interaction with the modep air H61-H62 are given. A pulse output power of 78 kW is obtained for the gyrotron by simulation at the beam voltage of 40 kV with beam current of 10 A, velocity ratio of 1.3, and magnetic field of 3.6 T, corresponding to a beam-wave interaction efficiency of 39%.
2011,
23.
Abstract:
A W-band fundamental harmonic continuous wave single-cavity gyrotron oscillator with the operating mode TE02 has been designed according to the electron cyclotron maser theory of gyrotron with self-consistent nonlinear beam-wave interaction code. The simulation result shows that the output power and the electron efficiency of the designed gyrotron oscillator is 31.8 kW and 35%, respectively, on the basis of the electron beam with voltage 30 kV, current 3.0 A and velocity ratio 1.5. In addition, the design and simulation of the gyrotron oscillator’s collector has been finished with the help of PIC software. The simulation result indicates that the power density on the collector wall would be less than 500 W/cm2 by using auxiliary coils which can effectively shorten the axial size of the
A W-band fundamental harmonic continuous wave single-cavity gyrotron oscillator with the operating mode TE02 has been designed according to the electron cyclotron maser theory of gyrotron with self-consistent nonlinear beam-wave interaction code. The simulation result shows that the output power and the electron efficiency of the designed gyrotron oscillator is 31.8 kW and 35%, respectively, on the basis of the electron beam with voltage 30 kV, current 3.0 A and velocity ratio 1.5. In addition, the design and simulation of the gyrotron oscillator’s collector has been finished with the help of PIC software. The simulation result indicates that the power density on the collector wall would be less than 500 W/cm2 by using auxiliary coils which can effectively shorten the axial size of the
2011,
23.
Abstract:
Based on a relativistic magnetron(RM) which has six different cavities, a three-strip transparent cathode has been designed and fabricated to improve the output characteristics of the RM. Computer simulation and laboratory tests are used to compare outputs of RMs using coaxial cathode and transparent cathode, respectively. The computer simulation shows that the RM using transparent cathode has less electron bunching time, less start up time, higher efficiency, better optimized output spectrum and less mode competition. The laboratory tests show that the RM using transparent cathode obtains wider pulses in the same conditions of experiment. The result indicates that using transparent cathode can shorten the start up time of RM, which agrees with the computer simulation. Moreover, the experi
Based on a relativistic magnetron(RM) which has six different cavities, a three-strip transparent cathode has been designed and fabricated to improve the output characteristics of the RM. Computer simulation and laboratory tests are used to compare outputs of RMs using coaxial cathode and transparent cathode, respectively. The computer simulation shows that the RM using transparent cathode has less electron bunching time, less start up time, higher efficiency, better optimized output spectrum and less mode competition. The laboratory tests show that the RM using transparent cathode obtains wider pulses in the same conditions of experiment. The result indicates that using transparent cathode can shorten the start up time of RM, which agrees with the computer simulation. Moreover, the experi
2011,
23.
Abstract:
The article introduces the test of beam cross-section, focusing field and transmission rate of sheet beam klystron with Wiggler focusing. Characteristics of Wiggler focusing are analyzed and the test method of improving the transmission rate is obtained. The test results show that the transmission rate varies significantly when the same set of magnets are laid in different arrangements. The mismatch of beam and Wiggler field can even lead to a transmission rate of zero. The transmission rate for different field periods is obtained and the period of 9 mm is the best choice, which results in a good transmission rate under a relatively low voltage and a magnetic field of bad uniformity.
The article introduces the test of beam cross-section, focusing field and transmission rate of sheet beam klystron with Wiggler focusing. Characteristics of Wiggler focusing are analyzed and the test method of improving the transmission rate is obtained. The test results show that the transmission rate varies significantly when the same set of magnets are laid in different arrangements. The mismatch of beam and Wiggler field can even lead to a transmission rate of zero. The transmission rate for different field periods is obtained and the period of 9 mm is the best choice, which results in a good transmission rate under a relatively low voltage and a magnetic field of bad uniformity.
2011,
23.
Abstract:
A Ku-band magnetically insulated transmission line oscillator(MILO) is put forward with the theoretical analysis according to dispersion characteristics of slow wave structure. Compared with common MILOs, the Ku-band MILO designed has a choke cavity whose outer radius is increased to avoid the breakdown between cathode and anode. The resonant frequency of 13.536 GHz and loaded quality factor of 43 are obtained through numerical calculation of the open cavity model of MILO. Then the structure parameters are further optimized and the impact of diode voltage on output power and efficiency is investigated with 2.5 dimensional particle-in-cell simulation. High power microwave is generated from the optimized Ku-band MILO with the average output power of 3.69 GW, central frequency of 13.62 GHz an
A Ku-band magnetically insulated transmission line oscillator(MILO) is put forward with the theoretical analysis according to dispersion characteristics of slow wave structure. Compared with common MILOs, the Ku-band MILO designed has a choke cavity whose outer radius is increased to avoid the breakdown between cathode and anode. The resonant frequency of 13.536 GHz and loaded quality factor of 43 are obtained through numerical calculation of the open cavity model of MILO. Then the structure parameters are further optimized and the impact of diode voltage on output power and efficiency is investigated with 2.5 dimensional particle-in-cell simulation. High power microwave is generated from the optimized Ku-band MILO with the average output power of 3.69 GW, central frequency of 13.62 GHz an
2011,
23.
Abstract:
A high power millimeter wave generator has been investigated and improved by particle in cell(PIC) simulations and experiments. Overmoded slow wave structures(SWSs) were adopted to increase power capacity. In order to realize single mode and single frequency operation, one useful method for mode selection was used, i.e. to shift the operating point close to π mode of TM01 wave. Due to the adoption of overmoded SWSs and proper design of the device, the guiding magnetic field could be reduced. The experiments were carried out at the TORCH-01 accelerator. The produced microwave frequency was measured by dispersive line method, and the power was estimated by integrating over the radiation pattern in far field. Rectangular-shaped SWSs were used in primary design, and a 33.56 GHz millimeter wav
A high power millimeter wave generator has been investigated and improved by particle in cell(PIC) simulations and experiments. Overmoded slow wave structures(SWSs) were adopted to increase power capacity. In order to realize single mode and single frequency operation, one useful method for mode selection was used, i.e. to shift the operating point close to π mode of TM01 wave. Due to the adoption of overmoded SWSs and proper design of the device, the guiding magnetic field could be reduced. The experiments were carried out at the TORCH-01 accelerator. The produced microwave frequency was measured by dispersive line method, and the power was estimated by integrating over the radiation pattern in far field. Rectangular-shaped SWSs were used in primary design, and a 33.56 GHz millimeter wav
2011,
23.
Abstract:
With the increase in frequency, the output gain and bandwidth of microwave vacuum devices are subject to considerable limitations, which may be solved by extended interaction klystron. With the same working principle as high-power klystron’s, the extended interaction klystron uses distribution function cavity technology to expand its operating bandwidth and gain. In this paper, a Ku-band extended interaction klystron tube is designed and simulated with PIC (particle-in-cell) three-dimensional software and CST. At the working voltage of 30 kV, beam current of 8.5 A, when the PPM-Focusing system of 0.48 T is adopted, and the input power is 5.1 W, the microwave output can be obtained with an efficiency of 23%, peak power of 58 kW, 3 dB bandwidth of 306 MHz, and the largest in-band gain of 39
With the increase in frequency, the output gain and bandwidth of microwave vacuum devices are subject to considerable limitations, which may be solved by extended interaction klystron. With the same working principle as high-power klystron’s, the extended interaction klystron uses distribution function cavity technology to expand its operating bandwidth and gain. In this paper, a Ku-band extended interaction klystron tube is designed and simulated with PIC (particle-in-cell) three-dimensional software and CST. At the working voltage of 30 kV, beam current of 8.5 A, when the PPM-Focusing system of 0.48 T is adopted, and the input power is 5.1 W, the microwave output can be obtained with an efficiency of 23%, peak power of 58 kW, 3 dB bandwidth of 306 MHz, and the largest in-band gain of 39
2011,
23.
Abstract:
A moderate-energy P-band relativistic backward wave oscillator (RBWO) is proposed and investigated by using the 2.5D fully electromagnetic particle-in-cell code, KARAT. A double corrugated configuration is designed in the coaxial slow wave structure (SWS) of the moderate-energy P-band RBWO, and thus enlarges the temporal growth rate and the beam-wave interaction space of the RBWO, resulting in larger power capacity and shorter microwave output saturation time. The presented P-band RBWO has an increase of about two times compared with the conventional one in the radial range of the beam-wave interaction space, with almost the same period of SWS. The simulation results show that a microwave with the power of 267 MW, frequency of 867 MHz and efficiency of 30% is obtained with the diode voltag
A moderate-energy P-band relativistic backward wave oscillator (RBWO) is proposed and investigated by using the 2.5D fully electromagnetic particle-in-cell code, KARAT. A double corrugated configuration is designed in the coaxial slow wave structure (SWS) of the moderate-energy P-band RBWO, and thus enlarges the temporal growth rate and the beam-wave interaction space of the RBWO, resulting in larger power capacity and shorter microwave output saturation time. The presented P-band RBWO has an increase of about two times compared with the conventional one in the radial range of the beam-wave interaction space, with almost the same period of SWS. The simulation results show that a microwave with the power of 267 MW, frequency of 867 MHz and efficiency of 30% is obtained with the diode voltag
2011,
23.
Abstract:
For a traditional collector of an S-band backward-wave oscillator, the affected area due to bombardment by energetic electrons was experimentally measured, and the power per unit area as thermal loading for a 700 keV and 7 kA beam with 50 ns duration was calculated. By using an ANSYS-APDL package, the 10 to 100 Hz repetitive operation results of temperature history and distribution of the collector were typically presented at convective coefficient of 7 000 W/(m2·℃) and water temperature of 20℃. The relationship between the equilibrium temperature and convective coefficient for different pulse repetition rate was also obtained. In addition, the cooling flow rate corresponding to different convective coefficient was given.
For a traditional collector of an S-band backward-wave oscillator, the affected area due to bombardment by energetic electrons was experimentally measured, and the power per unit area as thermal loading for a 700 keV and 7 kA beam with 50 ns duration was calculated. By using an ANSYS-APDL package, the 10 to 100 Hz repetitive operation results of temperature history and distribution of the collector were typically presented at convective coefficient of 7 000 W/(m2·℃) and water temperature of 20℃. The relationship between the equilibrium temperature and convective coefficient for different pulse repetition rate was also obtained. In addition, the cooling flow rate corresponding to different convective coefficient was given.
2011,
23.
Abstract:
This paper analyzes and simulates the RF breakdown in relativistic backward wave oscillator(RBWO). The RF breakdown which occurs on the surface of resonant reflector and slow wave structure(SWS) is induced by field emission. A method is proposed for reducing the surface field intensity, which utilizes cascade feedback reflector and trapezoid SWS with chamfering. The trapezoid SWS is axially lengthened at the minimum radius place for weakening field intensity so that the power capability of RBWO is increased availably. Simulation results indicate that the field intensity reduces from 1 400 to 570 kV/cm on the cascade feedback reflector, and from 1 100 to 780 kV/cm on the trapezoid SWS. Experiment results indicate that the microwave power and the pulse duration increase. A microwave with a p
This paper analyzes and simulates the RF breakdown in relativistic backward wave oscillator(RBWO). The RF breakdown which occurs on the surface of resonant reflector and slow wave structure(SWS) is induced by field emission. A method is proposed for reducing the surface field intensity, which utilizes cascade feedback reflector and trapezoid SWS with chamfering. The trapezoid SWS is axially lengthened at the minimum radius place for weakening field intensity so that the power capability of RBWO is increased availably. Simulation results indicate that the field intensity reduces from 1 400 to 570 kV/cm on the cascade feedback reflector, and from 1 100 to 780 kV/cm on the trapezoid SWS. Experiment results indicate that the microwave power and the pulse duration increase. A microwave with a p
2011,
23.
Abstract:
A modified helically corrugated waveguide was investigated for passive pulse compression with high gain and high efficiency, and its loss coefficient was obtained by employing the method of perturbation of Maxwell’s equations. According to the dispersion characteristics and loss coefficient of this waveguide, the optimum frequency sweep mode of input microwave pulse was designed, and the passive compression was simulated. This simulation demonstrates that a microwave pulse of 66 ns duration can be compressed into a 1.9 ns pulse with a power compression ratio of 21.2, a time compression ratio of 34.7 and an efficiency of 61%.
A modified helically corrugated waveguide was investigated for passive pulse compression with high gain and high efficiency, and its loss coefficient was obtained by employing the method of perturbation of Maxwell’s equations. According to the dispersion characteristics and loss coefficient of this waveguide, the optimum frequency sweep mode of input microwave pulse was designed, and the passive compression was simulated. This simulation demonstrates that a microwave pulse of 66 ns duration can be compressed into a 1.9 ns pulse with a power compression ratio of 21.2, a time compression ratio of 34.7 and an efficiency of 61%.
2011,
23.
Abstract:
The paper proposes a coupling probe which can effectively expand the coupling adjustment range, and optimally designs a 64-element array antenna’s rectangular radial line feed network at the center frequency of 2.1 GHz. Simulation results show that the feed network whose caliber is 744 mm×744 mm can achieve approximately 64-road equiamplitude feed. The reflection coefficient is less than 0.1 at the center frequency, and less than 0.2 in the frequency band ranging from 2.06 GHz to 2.15 GHz.
The paper proposes a coupling probe which can effectively expand the coupling adjustment range, and optimally designs a 64-element array antenna’s rectangular radial line feed network at the center frequency of 2.1 GHz. Simulation results show that the feed network whose caliber is 744 mm×744 mm can achieve approximately 64-road equiamplitude feed. The reflection coefficient is less than 0.1 at the center frequency, and less than 0.2 in the frequency band ranging from 2.06 GHz to 2.15 GHz.
2011,
23.
Abstract:
Considering region segmentation, message transmission, load balancing, synchronization, etc, the paper presents a parallel finite-difference time-domain algorithm to calculate the electromagnetic scattering at randomly rough surface and applies the algorithm to high performance parallel computers. Theoretical analysis and simulation show that, the algorithm can calculate electromagnetic scattering at large-scale random rough ground fast and efficiently. Its correctness and feasibility are verified by comparison with analytic method under the same conditions, and its large-scale results are better to reflect the ground statistical characteristics.
Considering region segmentation, message transmission, load balancing, synchronization, etc, the paper presents a parallel finite-difference time-domain algorithm to calculate the electromagnetic scattering at randomly rough surface and applies the algorithm to high performance parallel computers. Theoretical analysis and simulation show that, the algorithm can calculate electromagnetic scattering at large-scale random rough ground fast and efficiently. Its correctness and feasibility are verified by comparison with analytic method under the same conditions, and its large-scale results are better to reflect the ground statistical characteristics.
2011,
23.
Abstract:
The eigenequation of coaxial waveguide with inner and outer slotted structure is derived using the fields matching method, and the outer slotted cylindrical waveguide eigenequation is derived as well. Numerical simulation is conducted on the propagation characteristics of 2π mode in the inner and outer slotted structure and the outer slotted structure. The relationship between slot depths and eigenvalues of both structures is discussed, as well as the relationship between frequency and radiuses in the former structure. The results reveal that, the eigenvalue of inner and outer slotted waveguide increases with deeper inner slot, and decreases with deeper outer slot. The waveguide frequency is almost independent of inner radiuses, but is significantly affected by outer radiuses.
The eigenequation of coaxial waveguide with inner and outer slotted structure is derived using the fields matching method, and the outer slotted cylindrical waveguide eigenequation is derived as well. Numerical simulation is conducted on the propagation characteristics of 2π mode in the inner and outer slotted structure and the outer slotted structure. The relationship between slot depths and eigenvalues of both structures is discussed, as well as the relationship between frequency and radiuses in the former structure. The results reveal that, the eigenvalue of inner and outer slotted waveguide increases with deeper inner slot, and decreases with deeper outer slot. The waveguide frequency is almost independent of inner radiuses, but is significantly affected by outer radiuses.
2011,
23.
Abstract:
A kind of high power microwave mode converter is designed, which is lowly over-moded with input and output wave-ports perpendicular to each other. The converter can convert TM01 mode in a circular waveguide to TE10 mode in a rectangular waveguide, and works in C-band with a central frequency of 4.1 GHz. The results of simulation show that the energy conversion efficiency of the mode converter is up to 99% at 4.1 GHz, and the return loss is less than -20 dB. The bandwidth in which the conversion efficiency exceeds 90% is larger than 0.2 GHz. Its dimension is about 10 cm in each direction.
A kind of high power microwave mode converter is designed, which is lowly over-moded with input and output wave-ports perpendicular to each other. The converter can convert TM01 mode in a circular waveguide to TE10 mode in a rectangular waveguide, and works in C-band with a central frequency of 4.1 GHz. The results of simulation show that the energy conversion efficiency of the mode converter is up to 99% at 4.1 GHz, and the return loss is less than -20 dB. The bandwidth in which the conversion efficiency exceeds 90% is larger than 0.2 GHz. Its dimension is about 10 cm in each direction.
2011,
23.
Abstract:
The array antenna control system uses real-time operation system VxWorks, and the control system computer communicates with the unit antenna through peripheral component interconnect(PCI) device. This paper develops a PCI device driver based on VxWorks real-time operation system. The main tasks finished include the modification of board support package, the initialization of device registers and the design of performance functions. The test proves that the driver is stable and reliable, and can be applied in the control system.
The array antenna control system uses real-time operation system VxWorks, and the control system computer communicates with the unit antenna through peripheral component interconnect(PCI) device. This paper develops a PCI device driver based on VxWorks real-time operation system. The main tasks finished include the modification of board support package, the initialization of device registers and the design of performance functions. The test proves that the driver is stable and reliable, and can be applied in the control system.
2011,
23.
Abstract:
The paper developed a high-power microwave ultra-wideband coaxial rotary joint, and made some experimental study on its mechanical characteristics, temperature adaptability, transmission efficiency and power capability. The joint can work normally in the temperature range from -15 to 50 ℃. Fed in a pulse of 3 ns duration, it can realize a dynamic transmission efficiency of electric voltage of 99.14% with good stability. It can transmit transient pulses with ultra-wideband, peak power of 50 GW, repetition frequency of 100 Hz, and continuous action duration of 60 s. This rotary joint has been successfully applied to ultra-wideband vehicle-borne systems.
The paper developed a high-power microwave ultra-wideband coaxial rotary joint, and made some experimental study on its mechanical characteristics, temperature adaptability, transmission efficiency and power capability. The joint can work normally in the temperature range from -15 to 50 ℃. Fed in a pulse of 3 ns duration, it can realize a dynamic transmission efficiency of electric voltage of 99.14% with good stability. It can transmit transient pulses with ultra-wideband, peak power of 50 GW, repetition frequency of 100 Hz, and continuous action duration of 60 s. This rotary joint has been successfully applied to ultra-wideband vehicle-borne systems.
2011,
23.
Abstract:
This article uses VHDL to design a stepping motor control IP core based on FPGA which has been compiled and simulated in Quartus Ⅱ. This core calculates control parameters online, enabling every motor in the array to figure out its velocity profile and moments to send pulses in real time. At the same time, it can reduce the risk of losing steps. This IP core can handle the feedback signals from the encoder to judge and regulate step losses. The compilation result shows this IP core reduces the hardware resource consumed in real time calculation. The simulation result shows this IP core can achieve array antenna successive scanning.
This article uses VHDL to design a stepping motor control IP core based on FPGA which has been compiled and simulated in Quartus Ⅱ. This core calculates control parameters online, enabling every motor in the array to figure out its velocity profile and moments to send pulses in real time. At the same time, it can reduce the risk of losing steps. This IP core can handle the feedback signals from the encoder to judge and regulate step losses. The compilation result shows this IP core reduces the hardware resource consumed in real time calculation. The simulation result shows this IP core can achieve array antenna successive scanning.
2011,
23.
Abstract:
The paper proposes a conformal equiangular spiral antenna on the circularly truncated cone with electromagnetic band-gap structure(EAS-EBG antenna), which shows wideband characteristics with respect to the gain. Firstly, a conformal equiangular spiral antenna on the circularly truncated cone(EAS antenna) is modeled and analyzed by using the professional software HFSS. Next, the EAS-EBG antenna is studied, which inserts a small area of electromagnetic band-gap(EBG) structure into the circularly truncated cone to remain conformal and increase gain. The simulation shows that the antenna gain increases about 1 to 3 dB within the frequency range from 5 to 12 GHz and the axial ratio remains almost unchanged.
The paper proposes a conformal equiangular spiral antenna on the circularly truncated cone with electromagnetic band-gap structure(EAS-EBG antenna), which shows wideband characteristics with respect to the gain. Firstly, a conformal equiangular spiral antenna on the circularly truncated cone(EAS antenna) is modeled and analyzed by using the professional software HFSS. Next, the EAS-EBG antenna is studied, which inserts a small area of electromagnetic band-gap(EBG) structure into the circularly truncated cone to remain conformal and increase gain. The simulation shows that the antenna gain increases about 1 to 3 dB within the frequency range from 5 to 12 GHz and the axial ratio remains almost unchanged.
2011,
23.
Abstract:
The paper conducts the 3D simulation of microwave pulses propagating, reflecting and transmitting in a building, to analyze the distribution of the maximum value of electric field in time domain. For narrow-band modulated square pulses with different incident angles, the size of field enhancement region is in direct proportion to the size of region irradiated by microwaves directly through the windows and doors, and the size of windows exerts great influence upon the the size of field enhancement region. The field amplitude in the area behind windowsills reduces significantly in the propagation direction of microwave pulse. The pulse width has little influence upon the size of field enhancement region and the maximum value of electric field. For narrow-band modulated square pulses with zer
The paper conducts the 3D simulation of microwave pulses propagating, reflecting and transmitting in a building, to analyze the distribution of the maximum value of electric field in time domain. For narrow-band modulated square pulses with different incident angles, the size of field enhancement region is in direct proportion to the size of region irradiated by microwaves directly through the windows and doors, and the size of windows exerts great influence upon the the size of field enhancement region. The field amplitude in the area behind windowsills reduces significantly in the propagation direction of microwave pulse. The pulse width has little influence upon the size of field enhancement region and the maximum value of electric field. For narrow-band modulated square pulses with zer
2011,
23.
Abstract:
The analysis code for quasi-optical mode converter is developed based on the theory of vector diffraction and the self-adapted Katsenelenbaum-Semenov algorithm for phase correcting. A 3 mm-band quasi-optical mode converter (TE62 to TEM00) is then optimized, and corresponding parameters of its components, i.e. Vlasov radiator and phase correcting mirror, are obtained. A sample is fabricated accordingly, and tests are conducted. The theoretical results show that the output mode purity of the converter is larger than 94%. The experimental results agree well with the theoretical ones.
The analysis code for quasi-optical mode converter is developed based on the theory of vector diffraction and the self-adapted Katsenelenbaum-Semenov algorithm for phase correcting. A 3 mm-band quasi-optical mode converter (TE62 to TEM00) is then optimized, and corresponding parameters of its components, i.e. Vlasov radiator and phase correcting mirror, are obtained. A sample is fabricated accordingly, and tests are conducted. The theoretical results show that the output mode purity of the converter is larger than 94%. The experimental results agree well with the theoretical ones.
2011,
23.
Abstract:
Scattering characteristics of reflex metal grating are analyzed according to mode-matching method and space Floquet mode theory. Rectangular metal gratings are designed and optimized. The optimized double U-shaped gratings’ bandwidth is three times that of the rectangular ones, and the power capacity is 15 times. The CST simulation results show that the axial ratio of the circular polarization devices is 1.07 at the center frequency of 94 GHz, and right-handed circular polarization is realized.
Scattering characteristics of reflex metal grating are analyzed according to mode-matching method and space Floquet mode theory. Rectangular metal gratings are designed and optimized. The optimized double U-shaped gratings’ bandwidth is three times that of the rectangular ones, and the power capacity is 15 times. The CST simulation results show that the axial ratio of the circular polarization devices is 1.07 at the center frequency of 94 GHz, and right-handed circular polarization is realized.
2011,
23.
Abstract:
Based on mode coupling theory, coupling coefficients of TEM coaxial waveguide mode to TE11 mode have been derived theoretically, and the design of coaxial waveguide bend for transmitting TE11 mode is reported. The computer simulation via commercial software, based on finite-element method, shows that the TE11 mode transmission efficiency of the optimized coaxial waveguide bends have reached 99.5% at 0.680, 1.575 and 3.750 GHz. Moreover, the bandwidths in which the transmission efficiency exceeds 90% are 0.60 to 0.83 GHz, 1.10 to 2.42 GHz and 3.10 to 4.16 GHz, respectively. The power handling capacity has reached GW level.
Based on mode coupling theory, coupling coefficients of TEM coaxial waveguide mode to TE11 mode have been derived theoretically, and the design of coaxial waveguide bend for transmitting TE11 mode is reported. The computer simulation via commercial software, based on finite-element method, shows that the TE11 mode transmission efficiency of the optimized coaxial waveguide bends have reached 99.5% at 0.680, 1.575 and 3.750 GHz. Moreover, the bandwidths in which the transmission efficiency exceeds 90% are 0.60 to 0.83 GHz, 1.10 to 2.42 GHz and 3.10 to 4.16 GHz, respectively. The power handling capacity has reached GW level.
2011,
23.
Abstract:
The scattering properties and regularity of high power microwave propagation on the jungle-ground are analyzed with finite difference time domain (FDTD) method. The scattering properties at different incident angles are obtained, and the relationship between jungle scattering coefficient and grazing angle are comparatively analyzed with analytic and numerical methods. The theoretical analysis and numerical computation indicate that the scattering coefficient curve has a Brewster angle. Larger electrical parameters of topography lead to smaller Brewster angle. When the grazing angle is less than the Brewster angle, the scattering coefficient decreases with the grazing angle increasing; when the grazing angle is greater than the Brewster angle, the scattering coefficient increases with the
The scattering properties and regularity of high power microwave propagation on the jungle-ground are analyzed with finite difference time domain (FDTD) method. The scattering properties at different incident angles are obtained, and the relationship between jungle scattering coefficient and grazing angle are comparatively analyzed with analytic and numerical methods. The theoretical analysis and numerical computation indicate that the scattering coefficient curve has a Brewster angle. Larger electrical parameters of topography lead to smaller Brewster angle. When the grazing angle is less than the Brewster angle, the scattering coefficient decreases with the grazing angle increasing; when the grazing angle is greater than the Brewster angle, the scattering coefficient increases with the
2011,
23.
Abstract:
In order to achieve beam scanning of mechanical phased array antenna, the brushed DC motor (BDCM) is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. The paper uses the digital signal processor (DSP) TMS320F2812 to implement the position control system of BDCM, and describes the hardware design, control strategy and software design of the control system. In order to achieve fast and no overshoot response, the fuzzy proportional integral derivative(PID) control algorithm is researched and applied to the control system. Experiment results indicate that the position control system of BDCM is simple, and has good control performance, which can meet the requirements of fast and accurate phase control of the helical antenna element.
In order to achieve beam scanning of mechanical phased array antenna, the brushed DC motor (BDCM) is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. The paper uses the digital signal processor (DSP) TMS320F2812 to implement the position control system of BDCM, and describes the hardware design, control strategy and software design of the control system. In order to achieve fast and no overshoot response, the fuzzy proportional integral derivative(PID) control algorithm is researched and applied to the control system. Experiment results indicate that the position control system of BDCM is simple, and has good control performance, which can meet the requirements of fast and accurate phase control of the helical antenna element.
2011,
23.
Abstract:
Two improvements in the iteration method for mode converter design are presented, i.e. a reasonable initial step value in every iteration is given and coupled lines of less contribution are ignored to improve bandwidth. A TE01-TE11 mode converter is designed with the improved iteration method, whose ratio of waveguide radius to free space wavelength is 2.765 5. Simulation results show that its relative bandwidth reaches 6%, total length is 600 mm, and conversion efficiency is 99.14% at the central frequency. The total calculation time is 40 s. The CST simulation result agrees well with the coupled mode simulation one.
Two improvements in the iteration method for mode converter design are presented, i.e. a reasonable initial step value in every iteration is given and coupled lines of less contribution are ignored to improve bandwidth. A TE01-TE11 mode converter is designed with the improved iteration method, whose ratio of waveguide radius to free space wavelength is 2.765 5. Simulation results show that its relative bandwidth reaches 6%, total length is 600 mm, and conversion efficiency is 99.14% at the central frequency. The total calculation time is 40 s. The CST simulation result agrees well with the coupled mode simulation one.
2011,
23.
Abstract:
The paper analyzes the response equation of TEM horn to Gaussian pulse based on the theory of transmission line. The dependence of TEM horn’s response on its open angle is numerically studied under the excitation of Gaussian pulse and its differential, respectively, according to the tail fluctuation and negative peak undershoot in response. The experiments are conducted based on the time-domain test system with cone TEM cell. The results show that, for differential Gaussian pulse of 1 ns bottom-width, the negative peak undershoot increases from 1.0% to 3.6%, as the open angle varies from 8° to 20°. The experimental results are consistent with theoretical analysis and numerical simulation.
The paper analyzes the response equation of TEM horn to Gaussian pulse based on the theory of transmission line. The dependence of TEM horn’s response on its open angle is numerically studied under the excitation of Gaussian pulse and its differential, respectively, according to the tail fluctuation and negative peak undershoot in response. The experiments are conducted based on the time-domain test system with cone TEM cell. The results show that, for differential Gaussian pulse of 1 ns bottom-width, the negative peak undershoot increases from 1.0% to 3.6%, as the open angle varies from 8° to 20°. The experimental results are consistent with theoretical analysis and numerical simulation.
Characteristics of pyramidal horn used in high power microwave radiation field measurement at X-band
2011,
23.
Abstract:
The gain of pyramidal horns with different configurations was simulated and the high power microwave(HPM) measurement antenna with low gain was selected accordingly. The numerical simulation and experiment were carried out on the pyramidal horn’s pulse response and gain with and without flange and waveguide. The selected pyramidal horn will not distort the waveform of the short microwave pulse with 20 ns pulse width, and thus it can be used in the measurement of short microwave pulse. The influence of the flange and the 300 mm waveguide on the gain is less than 0.2 dB. Moreover, the pattern of the pyramidal horn is smooth and the beam width is about 50° for HPM measurement. The selected pyramidal horn is qualified for high power microwave radiation field measurement in complicated enviro
The gain of pyramidal horns with different configurations was simulated and the high power microwave(HPM) measurement antenna with low gain was selected accordingly. The numerical simulation and experiment were carried out on the pyramidal horn’s pulse response and gain with and without flange and waveguide. The selected pyramidal horn will not distort the waveform of the short microwave pulse with 20 ns pulse width, and thus it can be used in the measurement of short microwave pulse. The influence of the flange and the 300 mm waveguide on the gain is less than 0.2 dB. Moreover, the pattern of the pyramidal horn is smooth and the beam width is about 50° for HPM measurement. The selected pyramidal horn is qualified for high power microwave radiation field measurement in complicated enviro
2011,
23.
Abstract:
The paper studied the array method for the measurement of X-Band high power microwave(HPM) feed total radiation power. The radiation field of an X-band HPM feed was simulated to determine three key parameters of surface integral method, and the measurement error caused by the integral method was estimated. An array with 8 probes was designed to enhance the power density measurement precision and stability, with each probe carefully tested and calibrated. The measurement result shows that, the pulse waveforms obtained by different probes are almost the same; the power density measurement difference of 3 shots obtained by the same probe is within ±0.1 dB; the power density measurement difference of the 8 different probes is within ±0.3 dB. Cold and hot tested patterns of the feed agree wit
The paper studied the array method for the measurement of X-Band high power microwave(HPM) feed total radiation power. The radiation field of an X-band HPM feed was simulated to determine three key parameters of surface integral method, and the measurement error caused by the integral method was estimated. An array with 8 probes was designed to enhance the power density measurement precision and stability, with each probe carefully tested and calibrated. The measurement result shows that, the pulse waveforms obtained by different probes are almost the same; the power density measurement difference of 3 shots obtained by the same probe is within ±0.1 dB; the power density measurement difference of the 8 different probes is within ±0.3 dB. Cold and hot tested patterns of the feed agree wit
