A direct-conversion W-CDMA front-end SiGe receiver chip

Abstract

A W-CDMA direct-conversion front-end receiver chip consisting of a low-noise amplifier (LNA), a dual-gain RF variable-gain amplifier (RF-VGA), two direct-down-conversion mixers, a I/Q quadrature generator, and a base-band five-gain-stage VGA is designed and manufactured in a 0.25 /spl mu/m IBM SiGe BiCMOS production process. A very low DC offset value (<300 /spl mu/V) is measured at the output of the mixers as the LO signal is fed into the chip at twice the RF frequency. An extremely low local oscillator (LO) leakage of -105 dBm is measured at the LNA input, partly due to the excellent LO-to-RF isolation provided by the RF-VGA and the direct-conversion mixers. The measured cascaded noise figure for the chip (including the SAW filter) is 4.3 dB at the maximum gain mode, and the IIP2 and IIP3 are +37 and -16.5 dBm, respectively. The I/Q channels exhibit a small mismatch in magnitude (<0.1 dB) and in phase (1/spl deg/-1.5/spl deg/). The chip draws 24.9 mA from a 2.85V supply. The overall chip performance meets all the essential parameters of W-CDMA receiver front-end specs.