Polyphase filterbanks for symbol timing synchronization in sampled data receivers

Symbol timing synchronization is an important component in a receiver designed to recover data from a digitally modulated waveform. Current trends favor sampled data architectures to perform the synchronization, matched filtering, and detection required to recover the data. Symbol timing synchronizers in a sampled data receiver differ from their continuous-time counterparts: the functionality in a sampled data receiver is an adaptive interpolator as opposed to a sample and hold. This paper describes the use of a polyphase filter bank for symbol timing synchronizers in sampled data receivers. Using this approach, interpolation and matched filtering are rolled into a single operation that requires less resources than separate filters for matched filtering and interpolation. Interpolations are realized by filter bank index selection. Since the filter bank index plays the role of the fractional interpolation interval, the same loop control techniques used in other sampled data synchronizers can be used. Maximum likelihood timing synchronization techniques as well as "early-late gate" techniques can be incorporated into the polyphase filter bank in a natural way.