Symbol timing synchronization of π / 4 - DQPSK signals using polyphase filterbanks

In this paper, the use of a polyphase filterbank with the Gardner timing error detection (TED) algorithm for symbol timing synchronization of the π / 4-shifted differentially encoded quadrature phase shift keying (π / 4-DQPSK) modulation signal is investigated. The open loop S-curve and normalized power spectral density (PSD) of the simulated baseband modem incorporating the Gardner TED are presented. Acquisition and tracking performance indicate that this algorithm can also be used with the π / 4-DQPSK modulation scheme to detect the timing error in the presence of additive white Gaussian noise (AWGN).