A Low-Noise and Low-Power Frequency Synthesizer Using Offset Phase-Locked Loop in 0.13- $\mu{\rm m}$ CMOS

In this letter, a fractional-N frequency synthesizer based on an offset phase-locked loop (OPLL) architecture is presented. The proposed synthesizer achieves low-noise as the two low-pass filters that are inherent in the OPLL highly suppresses the quantization noise from the delta-sigma modulator. In addition, it consumes low power by employing charge-recycling technique in the sub-PLL. A prototype synthesizer implemented in 0.13 μm CMOS process achieves 9 dB of noise reduction compared to a conventional PLL while consuming 3.2 mW of power.