Investigation on the resonance observed in the embedding-impedance response of an 850-GHz waveguide HEB mixer

A resonance is observed while simulating the embedding-impedance response of an 850-GHz waveguide hot-electron-bolometer (HEB) mixer. At the resonance frequency strong electric field is found distributed in the dc-grounded branch of the mixer´s radio frequency (RF) choke filter. In fact, the phase response of the input reflection coefficient of the dc-grounded branch demonstrates the same resonance. Furthermore, the resonance frequency shifts with the change of the dc-ground position. A 254-times scale model of the dc-grounded branch of the mixer´s RF choke filter is fabricated and measured. Experimental results are found in good agreement with the simulation results.