Design of ultra-wideband Gaussian pulse source for ground penetrating radar
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摘要: 脉冲源作为探地雷达的核心部件，其高功率和超宽频带可保证探测距离和探测分辨率，波形的光滑性与稳定性同时也影响着目标成像质量。选用雪崩三极管组成Marx电路输出单极性脉冲，采取措施优化波形中的不光滑部分，精确计算传输线延迟时间，信号反向叠加形成双极性脉冲，设计梳状PCB形式有利于脉冲源的小型化。测量结果表明：脉冲波形平滑对称，正负峰间脉宽为1.64 ns，幅度为812 V(50 负载)，拖尾振荡低于总体幅值的10%，和仿真结果吻合较好，符合探地雷达的需求。Abstract: The pulse source is the hard-core in ground penetrating radar(GPR), whose high voltage and ultra-wideband assure surveying depth and accuracy. Besides that, the smoothness and stability of pulse waveforms also affect imaging quality. Avalanche transistors are chosen in the Marx circuit to produce unipolar pulses. Improving methods are put forward to remove the unsmoothness of pulse waveforms. Microstrip line is placed at the end of the circuit, and delay time occurred in it makes signals to be bipolar. Comblike PCB is available to minimize the pulse source. The measured results show that the width between minus peak and plus peak is 1.64 ns, the voltage value is 812 V (50 load resistance), and the trailer is less than 10% of the whole voltage value, which match the simulation results very well. The pulse source could meet the requirements of GPR.
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Key words:
- ground penetrating radar /
- ultra-wideband /
- pulse source /
- avalanche transistor /
- Marx circuit
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