A 0.13 m CMOS fractional-N frequency synthesizer for WLAN transceivers

Abstract: A fractional-N frequency synthesizer fabricated in a 0.13 m CMOS technology is presented for the application of IEEE 802.11 b/g wireless local area network (WLAN) transceivers. A monolithic LC voltage con-trolled oscillator (VCO) is implemented with an on-chip symmetric inductor. The fractional-N frequency divider consists of a pulse swallow frequency divider and a 3rd-order multistage noise shaping (MASH) modulator with noise-shaped dithering techniques. Measurement results show that in all channels, phase noise of the synthe-sizer achieves –93 dBc/Hz and –118 dBc/Hz in band and out of band respectively with a phase-frequency detector (PFD) frequency of 20 MHz and a loop bandwidth of 100 kHz. The integrated RMS phase error is no more than 0.8. The proposed synthesizer consumes 8.4 mW from a 1.2 V supply and occupies an area of 0.86 mm2. Key words: WLAN IEEE 802.11 b/g; frequency synthesizer; voltage controlled oscillator; modulator DOI: 10.1088/1674-4926/32/10/105005 EEACC: 222