A millimeter-wave multifunction HEMT mixer

A monolithic chip with a single 80-mu m HEMT device, 1.25 x 3.0 mm(2) in si ze, has been tested as both a fundamental and a subharmonic mixer, With inp ut filter networks for K- and Q-bands providing two separate radio frequenc y/local oscillator (RF/LO) channels to the gate, the chip produces an IF si gnal from de to 4 GHz at the drain. The mixer operates in three independent modes with the highest conversion gain of 6.9 dB in K-band fundamental mod e, the best DSB noise figure of 4.4 dB in Q-band fundamental mode, and bett er than 20 dB of on-chip LO-to-RF isolation in Q-band subharmonic mode. In all three modes, the active mixer has shown positive conversion gain.