Design of a 183 GHz sub-harmonic mixer based on the accurate Schottky diodes circuit model

To minimize the inaccuracy of Schottky diode pair circuit model for sub-millimeter wave band mixer, full-wave analysis and circuit simulation were carried out to classify the signals in and out of diodes. Then a more precise modeling of the anti-parallel diode pair was proposed and applied to the circuits of sub-millimeter wave sub-harmonic mixers. To enhance the efficiency of simulation and optimization, a globally lumped element equivalent circuit of the mixer has been built based on the accurate diode model. A 183 GHz sub-harmonic mixer was designed and fabricated. The mixer exhibited less than 6.8 dB double side-band conversion loss and a mixer temperature of lower than 800 K over an RF band of 176-192 GHz using 2 mW of local oscillator power at 92 GHz. A minimum double side-band mixer conversion loss of 4.9 dB was measured at 182 GHz. The measured results agree well with the simulated ones.