A wideband phase modulation technique adopting Fractional-N Direct Digital Frequency Synthesizer

Abstract

In this paper, an open-loop phase modulator, called Fractional-N Direct Digital Frequency Synthesizer (DDFS), for polar transmitter is proposed to resolve the limited bandwidth problem occurred in the traditional phase-locked loop (PLL)-based phase modulator. Besides, an effective noise shaping quantization method is taken into account to attenuate the fractional-spurs introduced by Fractional-N DDFS. The worst case RMS EVM per burst of the modulator is 0.32% when performing 10-Mbps 16PSK.