Single-phase binary phase-shift keying, quadrature phase shift keying demodulators using an XOR gate as a phase detector

Abstract

A single-phase/single-loop multiple-phase-shift-keying (<em><span lang="EN-US">m</span></em><span lang="EN-US">-PSK)</span><span lang="EN-US"> demodulator is described. The demodulator relies on a linear range of an exclusive-OR (XOR) gate employed as a phase detector. The phase controller takes the average output from the XOR gate and performs a sub-ranging/re-scaling operation to provide an input signal to a voltage-controlled oscillator (VCO). The demodulator is truly modular which theoretically can be extended for an </span><em><span lang="EN-US">m</span></em><span lang="EN-US">-PSK signal. The proposed single-phase binary-/quadrature-PSK (BPSK/QPSK) demodulators have been implemented with low-cost discrete components. The core of the phase controller simply relies on number of stages of a full-wave rectifier and a linear amplifier built from well-known op-amp-based negative feedback circuits. The demodulator prototypes operate from a single supply of 5 V. At a carrier frequency of 100 kHz, both the BPSK and QPSK demodulators achieved the maximum symbol rate of 20 ksymbol/s respectively. At these symbol rates, the BPSK and QPSK demodulators deliver symbol-error rates less than 2×10<sup>-10 </sup>and 7×10<sup>-10</sup>.</span>