WCDMA direct-conversion receiver front-end comparison in RF-CMOS and SiGe BiCMOS

Wide-band code-division multiple-access direct-conversion receiver front-ends have been implemented in both 0.25-μm RF-CMOS and SiGe BiCMOS technologies. These circuits have been designed for the same application, radio architecture, and system specifications, allowing relevant comparisons to be made. The front-ends include a bypassable low-noise amplifier, a quadrature downconverter, baseband variable-gain amplifiers, and a local-oscillator frequency divider with output buffers. At 24.5 mA of total current consumption from a 2.7-3.3-V supply, the CMOS front-end has a noise figure of 5.3 dB, in-band third-order intercept point (IIP3) and second-order intercept point (IIP2) of -14 and +20.7 dBm, respectively, and out-of-band IIP3 and IIP2 of >+1.2 and +69 dBm, respectively. Compared to an SiGe front-end consuming 22 mA, the CMOS circuit has a 2-dB higher noise figure, comparable out-of-band linearity, 3-dB higher in-band IIP3, 12-dB lower in-band IIP2, and 7-dB higher LO-to-RF leakage.