A 5-GHz CMOS frequency synthesizer with an injection-locked frequency divider and differential switched capacitors

A phase-locked loop (PLL)-based frequency synthesizer at 5 GHz is designed and fabricated in 0.18-[micro]m CMOS technology. The power consumption of the synthesizer is significantly reduced by using an injection-locked frequency divider (ILFD) as the first frequency divider in the PLL feedback loop. The synthesizer chip consumes 18 mW of power, of which only 3.93 mW is consumed by the voltage-controlled oscillator (VCO) and the ILFD at 1.8-V supply voltage. The VCO has the phase noise of--104 dBc/Hz at 1-MHz offset and an output tuning range of 740 MHz. The chip size is 1.1 mm x 0.95 mm. Index Terms--Frequency divider, injection-locked frequency divider (ILFD), integer-N, low power, oscillator, phase-locked loop (PLL), receiver, synthesizer, voltage-controlled oscillator (VCO), wireless local area network (WLAN).