20-Mb/s GFSK Modulator Based on 3.6-GHz Hybrid PLL With 3-b DCO Nonlinearity Calibration and Independent Delay Mismatch Control

A hybrid two-point modulator which mitigates the nonlinearity problem of a digitally controlled oscillator (DCO) and provides a fine delay mismatch calibration is proposed for high data rate applications. A DCO with a separate high-pass modulation path in which only 3 b are used for a capacitor array is designed for flexible gain partition and simple nonlinearity calibration. A nonuniform multilev...