Efficient digital filters for pulse-shaping and jitter-free frequency error detection and timing recovery

Abstract

Digital Nyquist pulse-shaping filtering is an important application of multirate filtering techniques to communications signal processing. Nyquist pulse shaping is a crucial element in all bandwidth efficient digital communication systems utilizing linear modulation techniques. The square-root raised-cosine filter is the standard solution to this application, but it has been clearly demonstrated in the literature that optimized multirate filtering techniques provide significant improvement in the implementation complexity. FIR filters are commonly used in this application, but also efficient IIR filter structures have been presented. In this paper, we examine the properties of a certain interesting class of IIR filters which are composed of allpass subfilters. Their properties are compared with standard and optimized FIR filter designs. We also discuss how complementary FIR or IIR filter pairs can be utilized more generally in the front-end processing of digital receivers. We present an efficient receiver front-end architecture which combines with the receiver half-Nyquist filtering the special prefiltering required to achieve jitter-free performance in frequency-error detection and timing recovery.