Phase shift keying modulator design employing electronically controllable all-pass sections

Abstract

This paper presents two techniques of implementation of phase shift keying modulator. Both techniques are focused on the utilization of special features of an oscillator, which is based on first-order all-pass filters. The first method leads to modulators having generated signals with arbitrary phase shift between two outputs using only special features of oscillators in order to use less number of components in the structure. The second approach utilizes the same oscillator and also additional all-pass filter that increases the complexity of the circuitry, but eliminates requirements for extra-complicated driving circuit (control logic) and removes some undesired aspects of the first solution. The related circuits and subsystems are discussed in detail. Finally, features of all proposed structures are verified via PSpice using TSMC 0.18 um CMOS technology parameters and also by laboratory experiments with commercially available active devices. The experimental results agree both with simulation and theoretical analysis.