A miniature Q-band balanced sub-harmonically pumped image rejection mixer

This work presents a miniature Q-band balanced single side-band sub-harmonically pumped image rejection diode mixer (SHIRM) using a compact Marchand dual balun design. The SHIRM is realized employing four anti-parallel diode pairs for frequency mixing, a Lange coupler for radio frequency (RF) signal input, and a reduced size three-conductor-line Marchand dual balun for local oscillator pumping. The length of three-conductor-line dual balun is reduced by 81% after shunting two lumped capacitors at the center conductor. The measured results exhibit a minimum conversion loss of 8.6 dB, a maximum image rejection ratio of 22 dB, all ports isolation better than 37 dB, and an input 1-dB compression point of 2.5 dBm at RF bandwidth of 40.5 to 43.5 GHz and fixed intermediate frequency of 2.4 GHz. The chip area is very compact, only 1 × 0.84 mm².