A 17 mW, 2.5 GHz fractional-N frequency synthesizer for CDMA-2000

A 2.5 GHz fractional-N frequency synthesizer in 0.5- µm 15-GHz ftBiCMOS employs one-bit 4th-order ΣΔ modulator with multiple feedback and pulse-swallowed dual-modulus divider, resulting in simple architecture, less sensitivity to PLL nonlinearities, and lower out-of-band phase noise. Measurements, with a 3rd-order LPF, show -139 dBc/Hz phase noise at 1.2 MHz offset from carrier frequency of 1643 MHz and less than -87 dBc in-band fractional spurs. It consumes 5.5 mA at 3 V.