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A new symbol synchronizer with reduced timing jitter for QAM systems

A new and simple symbol synchronizer for QAM systems with reduced timing jitter is proposed. In the symbol synchronization loop, the timing error detection algorithm proposed by Gardner (1986) is used and a first order PLL is used for tracking optimal sampling instants. In a common first order PLL used in a symbol synchronizer, the loop filter gain is a constant, while in the reduced timing jitter symbol synchronizer, the loop filter gain is adaptively changed so that the timing jitter is greatly decreased. The scheme is also suitable for the case where burst transmissions take place. Furthermore, the mechanism of changing the loop filter gain is quite simple. The paper describes the new scheme and gives simulation results when the scheme is applied to a 16 QAM system. The simulation results show that the timing jitter is much smaller than when a constant loop filter gain is used.