Dual Function Mixer Circuit for Millimeter Wave Transceiver Applications

A monolithic mixer circuit capable of performing either a receiver or transmitter function has been fabricated. The mode of operation is determined by applying either forward bias or reverse bias to a pair of mixer diodes. The circuit integrates Schottky-barrier diodes, bias lines, Ta₂O₅ blocking and by-pass capacitors, a radial line stub filter and a microstrip branch-line coupler. For the receiver function the unit exhibits a conversion loss of 6.5 +- 0.5 dB from 34 to 36 GHz. For the transmitter function the circuit directs the signal from the local oscillator port to the antenna port with an insertion loss of approximately 2 dB at 33.5 GHz over a bandwidth of 1 GHz.