An Improved 110–130-GHZ Fix-Tuned Subharmonic Mixer with Compact Microstrip Resonant Cell Structure

This paper presents the design and fabrication of an improved low-loss 110–130 GHz subharmonically pumped mixer with planar Schottky diodes fabricated by Virginia Diodes Inc. The antiparallel pair of planar GaAs Schottky diodes flip-chipped onto a suspended microstrip is fully integrated with a radio frequency (RF) and an intermediate frequency (IF) filter. A compact microstrip resonant cell (CMRC) filter is for the first time introduced in a submillimeter mixer to replace the traditional low-and-high-impedance microstrip RF filter. The shorter size and wider stop-band of the CMRC filter improved the performance of the subharmonic mixer. The best single-sideband (SSB) conversion loss of 7.7 dB was achieved with 3.5 mW of local oscillator (LO) power at a fixed 59 GHz of LO frequency. Over an RF band of 20 GHz, the SSB conversion loss is below 11 dB.