Design of 425 GHz Sub-Harmonic Mixer

The terahertz receiver system has the characteristics of wide-band detection, and has a wide application prospect in the fields of space communication, meteorology research, inspection and detection. The development of superheterodyne receiver has certain advantages in the higher frequency band of terahertz. And the second harmonic mixer is the most widely used, with a good compromise effect. Based on the mature quartz circuit and shielded cavity processing technology, a 425 GHz sub-harmonic mixer is designed. The mixer is designed with anti-parallel Schottky diode with anode area of 0.64 μm2 to achieve lower junction capacitance and higher cut-off frequency. The circuit adopts the combination of microstrip line and suspended microstrip line, which not only realizes the good support of the circuit, but also reduces the loss caused by the dielectric substrate. The 425 GHz sub-harmonic mixer structure adopts the matching mode of four impedance lines to simplify the circuit structure. The overall circuit length is 3.069 mm.