An Aliasing-Free Receiver with Variable Sample Rate Digital Feedback M/T NDA Timing Synchronization

Abstract

The evolving digital television broadcasting standard does not standardize the data rate 1/T of the transmitted data but instead leaves it completely unspecified. We propose two digital receiver algorithms based on a free running oscillator (rate 1/T_s) for the processing of an extended range of variable sample rates T_s/T based on a timing synchronization algorithm producing synchronized samples at rate M/T where M is variable. It is shown that the well known timing error detector from Gardner[1] also works for M>2 which forms the basis of the timing synchronizer which is built similar to [2, 3]. Main issue for variable symbol rate receivers is to supress aliasing due to the different sampling rates in the receiver. One of the algorithms removes aliasing by filtering the received samples prior to timing synchronization and choosing M=2, whereas the second algorithm also uses the sample rate 3/T in the timing recovery loop and matched filter depending on T/T_s and thus avoids the necessity of prefiltering. The algorithms are compared in terms of their complexity, timing error variance and BER performance. Both algorithms can be implemented causing negligible loss in a DVB receiver.