Wideband subharmonic mixer in bilateral finline at U-band

A wideband subharmonically pumped mixer is presented and demonstrated at U-band. A wide bandwidth from 40 to 60 GHz is achieved by asymmetric bilateral finline and a pair of anti-parallel diodes. The local oscillator signal passes through a novel microstrip-to-finline transition to the bilateral finline, which is helpful to impedance match. The transition structure enables the mixer to conveniently integrate with monolithic microwave integrated circuits (MMIC). The compact subharmonic mixer is fabricated on 0.254 mm thick Rogers Duroid 5880 substrate, which is suspended in the E-plane of a standard rectangular waveguide WR-19. Measurement result shows its conversion loss is less than 15 dB from 40 to 60 GHz. The isolations between each port are higher than 40 dB.