5.7 GHz Gilbert I/Q downconverter integrated with a passive LO quadrature generator and an RF Marchand balun

Abstract

A 5.7 GHz I/Q downconversion mixer is demonstrated in this letter using 0.35 mu m 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 I/Q Gilbert mixer to generate balanced RF signals. All the reactive passive elements are placed directly on the standard silicon substrate. The 5.7 GHz I/Q downconverter achieves 7 dB conversion gain, -26 dBm IP1dB, and -18 dBm IIP3 at the power consumption of 3.875 mW and 2.5 V supply voltage.