Fully coherent shaped offset QPSK demodulator architecture with superior hardware efficiency

Abstract

Shaped Offset QPSK (SOQPSK) is a highly bandwidth-efficient constant envelope waveform. In order to increase hardware and energy efficiency, a new architecture for fully coherent SOQPSK demodulation is proposed that is suitable for continuous and burst mode transmission. It contains Decision-Directed (DD) synchronization loops for frequency, phase and timing offsets and a low complex method combining robust Start of Frame (SoF) detection with Phase Ambiguity Resolution (PAR) based on nested Barker codes. A coarse grained pipeline structure aims for minimal clock speeds and energy consumption while keeping the overall throughput high. Large complexity reductions are achieved by a multiplier-free Matched Filter (MF) design. Computer simulations and Field Programmable Gate Array (FPGA) implementation results show that the complexity-accuracy trade-offs have been reasonably chosen in terms of close-to-optimal Bit Error Rate (BER) performance and that hardware efficiency gains of more than 90 % compared with implementations from literature are achievable.