A 17-mW transmitter and frequency synthesizer for 900-MHz GSM fully integrated in 0.35-(mu)m CMOS

A fractional-N phase-locked loop (PLL) serves as a Gaussian minimum-shift keying (GMSK) transmitter and a receive frequency synthesizer for GSM. The entire transmitter/synthesizer is fully integrated in 0.35-(mu)m CMOS and consumes 17.4 and 12 mW from 2.5 V in the transmit and receive modes, respectively, including an on-chip voltage-controlled oscillator. The circuit meets GSM specifications on modulation accuracy in transmit mode, and measured phase noise from the closed-loop PLL is -148 dBc/Hz and -162 dBc/Hz, respectively, at 3- and 20-MHz offset. Worst case spur at 13-MHz offset is -77 dBc.