A compact carrier generation system enabling proper interoperability among quad-band GSM, WCDMA (FDD and TDD), and WLAN (802.11a/b/g) standards is developed. The implementation is achieved in 0.25-mum BiCMOS-SiGe process. The measured tuning range is higher that 1 GHz (3.05 to 4.1 GHz) exceeding the specifications by 25%. The voltage-controlled oscillator (VCO) exhibits a phase noise of -118 and -125 dBc/Hz measured, respectively, at 400 kHz and 1 MHz offsets while drawing 2.5 mA from 2.5 V supply. The measured phase noise at 400 kHz offset of the PCS/DCS output local-oscillator (LO) signal and the GSM output LO signal is, respectively, -124 dBc/Hz and -130 dBc/Hz