A broadband 630–720 GHz Schottky based sub-harmonic mixer using intrinsic resonances of hammer-head filter

An room temperature low noise anti-parallel Schottky diode based 630–720GHz sub-harmonic mixer (SHM) is designed, built and measured. Intrinsic resonances in low-pass hammer-head filter have been adopted to prevent the LO and RF power leak from the IF channel, while greatly minimizing the transmission line size. The mixer consists of 15um quartz terahertz circuit and 127um Al2O3 IF transformer circuit. An improved lumped element equivalent noise model of SBDs guarantees the accuracy of simulation. The measurement indicates that with local oscillating (LO) signal of 2–8 mW, the lowest double sideband (DSB) conversion loss is 8.2 dB at 645 GHz, and the best DSB noise temperature is 2800 K at 657GHz. The 3 dB bandwidth of conversion loss is 75 GHz from 638 to 715 GHz. The work IF frequency band is above 20GHz ranging from 1 to 20 GHz with −10dB return loss.