An Improved Gardner Feedback Timing Synchronization Loop

To compensate for signal damage during transmission and retrieve signal in coherent optical communication, the receiver side must be clock synchronized first. For the classic Gardner timing synchronization algorithm has disadvantages such as extended synchronization establishment time and algorithm failure when neighboring symbols have the same polarity, an improved Gardner feedback timing synchronization loop is proposed in this paper. First, the Lagrangian cubic interpolation filter is chosen for interpolation, and the polarity of the interpolated sequence is determined before it enters the timing error detector. The improved Gardner algorithm is then used selectively based on whether the adjacent symbols have the same polarity. The simulation objects are QPSK signals, and the simulation results demonstrate that the improved algorithm takes less time to reach synchronization, and the fractional interval and timing error converge faster than the classic Gardner approach, improving the loop's performance to some amount.