A Variable Conversion Gain Star Mixer for Ka-Band Applications

A variable conversion gain star mixer for Ka-band applications has been presented. This monolithic microwave integrated circuit was implemented on AlGaAs/InGaAs/GaAs pseudomorphic high-electron-mobility transistor process with a chip size of 1.7times1.7 mm
²
. The mixer is modified from conventional star mixer to apply dc bias. The conversion gain of the mixer, controlled by the voltage of the diodes, could be applied to meet gain compensation requirements in communication systems. From the measured results, the circuit can provide 11.9 dB conversion gain and 9.3 dB gain adjustment by controlling voltage from 0 to 0.7 V at 30 GHz.