A New FQPSK with Ideal BER Performance

Feher Quadrature Phase Shift Keying (FQPSK) has found wide application in deep-space communications and air-borne remote-sensing, due to its favorable features such as constant envelop and compact power spectral density (PSD). However, the optimum reception of FQPSK signals in AWGN channels calls for a highly-complex Viterbi equalizer, due to the inter-symbol interferences introduced by the FQPSK modulation. In this paper, we present a new Square-Root FQPSK (SR-FQPSK) by redefining the shaping filters of conventional FQPSK. Our research shows that SR-FQPSK inherits the desirable advantages of FQPSK, and more importantly, it yields to optimal BER performance when demodulated by a common OQPSK receiver.