Passive 8-16 GHz MMIC image-reject mixer

A passive 8-16 GHz MMIC image-reject mixer design is presented. The circuit, fabricated on a 4-mil GaAs substrate, is entirely passive and uses planar Schottky barrier diodes as the mixing elements. The topology is a phase-type configuration using two single-balanced mixers and in-phase and quadrature power dividers on-chip, with an off-chip IF quadrature combiner in the 0.1 ro 1.5 GHz band. This approach results in high process yields and excellent circuit uniformity. The design methodology and experimental results are described. A maximum conversion loss of 8 dB, greater than 20-dB image-rejection, and good return loss and port to port isolations were achieved using an 18-dBm LO (local oscillator) drive and an IF of 100 MHz.<>