Dual function mixer circuit for mm-wave transceiver applications

A monolithic mixer circuit capable of performing either a receiver function or a transmitter function has been fabricated. The mode of operation is determined by applying either forward or reverse bias to a pair of mixer diodes. The circuit integrates Schottky barrier diodes, bias lines, Ta2O5 blocking and bypass 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 + or - 0.5 dB in the 34 to 36 GHz range. For the transmitter function, the circuit directs the signal from the local oscillator port to the antenna port on the chip with insertion losses of approximately 1 dB at 33.5 GHz over a bandwidth of 1 GHz.