Filter coefficient interpolated timing recovery in sampled coherent PSK receivers

Timing recovery from input phase shift keying (PSK) receiver samples is considered for a Nyquist data transmission link. Adjustment of the timing phase of the input analog-to-digital (A/D) converter is not allowed, and thus timing recovery is based completely on received samples and is asynchronous with the A/D converter. To improve timing resolution over that provided by oversampling and decimation alone, the concept of filter coefficient interpolation is evaluated for a steam transmission, coherent, Nyquist-filtered, binary-PSK (BPSK) modem. This is a low-complexity, table lookup method that is useful in low-consumed-power radio modems. Performance is presented for E _b/N₀ down to 0 dB, and loop filtering is used to extend the threshold E_b/N₀ for successful receiver operation. The timing loop is shown analytically to converge in the mean-square sense. The training mode of the coherent modem, is discussed