A BBPLL-Based Demodulator with Multiphase and Feedforward Linearization Methods for Phase-Tracking Receivers

This paper describes a low-power multiphase bang-bang PLL (BBPLL) that performs oversampled noise-shaping demodulation as a secondary loop for phase-tracking receivers. A 31-phase BBPLL with a 16-stage ring voltage-controlled oscillator (VCO) is designed to achieve an adaptive loop gain control for a frequency-modulated input with a large frequency deviation. To reduce the effect of VCO nonlinearity on demodulation performance, a feedforward linearization method is proposed by scaling a modulation signal with an integral voltage of the loop filter. The proposed 50MHz divider-less BBPLL is designed in 65nm CMOS, consuming 0.7mW from a 1V supply. Simulation results verify that the multiphase and feedforward linearization methods improve demodulation performance for 5Mb/s BFSK signal with 10MHz deviation.