All-digital symbol timing recovery scheme utilizing efficient IIR prefiltering

Efficient IIR filter structures based on allpass subfilters have been presented earlier for Nyquist pulse shaping applications. In a previous paper, we presented a receiver front-end architecture which efficiently combines the half-Nyquist filtering and special prefiltering required to achieve jitter-free frequency-error detection. In this paper we utilize the same kind of prefiltering to develop an all-digital jitter-free symbol timing error tracker suitable for multiamplitude signals. The proposed structure is an approximation to a timing error tracker based on the maximum likelihood principle. It is also shown that fast convergence of the timing recovery loop can be achieved due to the short filter delay in the feedback loop