Single loop synthesizer and SDR modulator

Abstract

Software defined radios are becoming very popular due to their cost, size, and ability to create any waveforms. In this paper, we present a simpler software defined modulator for VHF radios based on a digital synthesizer that is composed of a single phase locked loop with a variable reference frequency. Existing synthesizers are limited to either small step-size with spurs as in fractional N architecture or large step-size with no spurs as in integer N architecture. Our proposed synthesizer has fast-lock time that is capable to work as a software modulator for phase and frequency in software defined radios, small phase noise, and no spurs. We used simulation to validate our approach and the results showed that it is superior to the existing synthesizer architectures.