A center-aligned digital pulse-width modulator for envelope modulation of polar transmitters

This paper presents a center-aligned hybrid digital pulse-width modulator for the envelope modulation of polar transmitters [1]. To obtain better noise figure of the outputs, a 128-phase delay-locked loop is used to generate center-aligned output pulses having 64 different pulse widths for 6-bit signal input. To reduce the number of delay cells in the multi-phase DLL, a simple counter is used to separate the output phases of DLL into rise and fall parts. The proposed digital pulse-width modulator is simulated in TSMC 90nm 1P9M process. The power consumption is 0.85 mW at a 92.16 MHz input reference frequency and a supply voltage of 1.2V.