Design and Experiments of a 160–200-GHz Broadband Quasi-Optical Schottky Subharmonic Mixer

This article presents a system design methodology and experimental validation of a 160–200-GHz broadband quasi-optical Schottky subharmonic mixer. To enhance the operating bandwidth, an on-chip local oscillator (LO) U-slot antenna for receiving the LO pumping signal and a radio frequency (RF) dual-patch antenna for receiving the RF signal are designed. Moreover, the LO and RF antennas are mounted on the front and back sides of the device, respectively. This arrangement simplifies the quasi-optical configuration. To improve integration and increase the isolation between the LO and intermediate frequency (IF) signals, a compact microstrip resonant cell (CMRC)-based low-pass filter (LPF) is incorporated. In addition, Huygens’ metalens is designed on a single substrate with only two metallic layers to converge the beam and increase the gain of the LO and RF antennas. Within the operating frequency range of 160–200-GHz, the measured single-sideband conversion loss ranges from 10.9 to 13.2 dB.