5.7 GHz Gilbert I/Q Downconverter Integrated With a Passive LO Quadrature Generator and an RF Marchand Balun

A 5.7 GHz downconversion mixer is demonstrated in this letter using 0.35 mum SiGe BiCMOS technology. A quarter-wavelength coupled line and two center-tapped transformers are utilized to generate differential quadrature LO signals. A miniaturized Marchand balun is placed before the common-base-configured RF input stage of each Gilbert mixer to generate balanced RF signals. All the reactive passive elements are placed directly on the standard silicon substrate. The 5.7 GHz downconverter achieves 7 dB conversion gain, 26dBm _1dB, and 18dBm IIP₃ at the power consumption of 3.875 mW and 2.5 V supply voltage.