A frequency synthesizer realized by a transformer-based voltage-controlled oscillator for IEEE 802.11a/b/g channels

A fractional-N frequency synthesizer for IEEE 802.11a/b/g standard with the design focused on voltage controlled oscillator (VCO) is proposed in this paper. Unlike the traditional approach of tuning VCO oscillation frequencies by capacitive varactors, the proposed VCO with a voltage-controlled inductor, which is made by an integrated transformer technology, is adopted. A digital delta-sigma modulator realized with FPGA verification is employed for fractional-N purpose to meet IEEE 802.11a/b/g channels. The frequency synthesizer is simulated in 0.18-/spl mu/m CMOS process with a loop-bandwidth of 300 KHz for a 32-MHz reference and the power dissipation is about 40 mW from a 1.8-V supply.