A SiGe RF front-end with on-chip VCO for a GPS receiver

A GPS direct conversion RF front-end with on-chip VCO fabricated in 0.35µm SiGe BiCMOS technology is presented. The properties of inductively degenerated common-emitter LNA and resistively degenerated Gilbert downconversion mixer are examined. The approximative equations for the front-end DSB-NF and IIP3 are given. By applying the derived formulas, the front-end performance can be readily estimated and optimized. The implemented RF front-end has a voltage conversion gain of 25.8 dB, DSB-NF of 2.7 dB, IIP3 of-14.5 dBm and IIP2 of +26 dBm. The 3.15 GHz VCO has a phase noise of -99 dBc/Hz at 100 kHz offset. The front-end draws 15.3 mA from a 2.7 V supply.