A V band singly balanced diode mixer for space application

The paper describes the design of a V band single balanced mixer to be employed in the front end of an on-board receiver for space applications. The V band receiver is a demonstrator for the use of different monolithic processes and interconnection/assembly technologies in space applications at such high frequencies. The receiver front-end consists of a multi-stage LNA amplification followed by an image reject filter, the mixer and a frequency doubler for the local oscillator. All the chips are mounted over an LTTC substrate using bumps/hot vias technology. Chip to chip interconnection is provided by coplanar wave guide on LTTC. The mixer employs a rat race 180 degrees hybrid to balance the local oscillator and a couple of Schottky diodes as mixing elements. The technology employed is a 0.15 mu m pHMET process that offers diodes with a cut off frequency higher that 300GHz. The choices made for the mixer type and topology starting from the system specifications are covered in the paper along with the actual description of the circuit design.