Broadband CMOS Gilbert Down-Converter utilizing a low-loss step-impedance rat-race coupler

A Broadband Gilbert Down-Converter with step-impedance rat-race coupler is demonstrated using 0.13 mum standard CMOS technology. The proposed method utilizes higher effective dielectric-constant, phase-inverter and step-impedance techniques simultaneously to make the rat-race coupler more compact (~ 64% reduction) and phase-balanced over a wide operating bandwidth. The down-converter has NF of 16 dB and LO-to-RF isolation of better than 35 dB. The mixer core consumes 2.9 mA at V_dd=1.8 V.