A Design of Equalization Digital On-Channel Repeater for Single Frequency Network ATSC System

This paper presents a guideline for designing an Equalization Digital On-Channel Repeater (EDOCR) and proposes an efficient method to implement it. The major concerns in the design of an EDOCR are shortening the system delay, maintaining synchronization between a main transmitter and an EDOCR, obtaining high signal to noise ratio (SNR) output, and enabling operation in an environment of adjacent channel interference. The short system delay is achieved adopting a demodulation scheme without an additional lowpass filter to remove harmonics, an intelligent slicer of a trellis decoder with a trace back depth of 1 for equalization, and an equi-ripple filter for the 8-VSB pulse shaping filter. To maintain the synchronization, the frequency offset information extracted from the received signal is reflected on a re-transmitting signal. Distinguished features of the EDOCR are adaptive equalization with the intelligent slicer which corrects symbol errors caused by on-air interface including the signal loopback, and the signal processing scheme which demodulates the received signal to a baseband symbol and re-modulates the symbol. Hence, the EDOCR can produce an exact replica of the main transmitter's signal with high SNR although there may be adjacent channels and input signal is distorted by multipath and noise. Finally, the performance evaluation of the designed EDOCR in both simulation and laboratory tests are presented and implementations of single frequency networks employing EDOCRs are discussed.