A SiGe active sub-harmonic front-end for 5-6 GHz direct-conversion receiver applications

This paper describes the design and measurement of a fabricated SiGe RF front-end for use in direct-conversion receivers for the Unlicensed National Information Infrastructure (U-NII) bands. The front-end is composed of an LNA, I and Q /spl times/2 sub-harmonic mixers (SHMs), and an LO conditioning chain. The receiver is completely differential and is designed for operation from a 3.3 V supply. The current consumption is /spl sim/6 mA for the LNA and /spl sim/5 mA for each mixer. The I/Q mixer pair alone (front-end without LNA) demonstrates /spl sim/8-10 dB gain and an IIP2 of /spl sim/+29 dBm in the lower U-NII bands. Measured receiver performance (with LNA) shows 18-20 dB conversion gain in the lower two U-NII bands, -16 dBm input compression point, and >10 dB return loss across all three U-NII bands.