改进的Gardner插值误差捕获符号同步算法研究

Research on Improved Gardner Symbol Rate Synchronization Algorithm with Interpolation Error Capture

数字通信系统中,同步是必不可少的环节。收发端采用不同的时钟信号,但需要步调一致地协调工作,必须通过同步系统来保证。同步系统工作性能的好坏,很大程度上决定了通信系统的质量。针对接收机存在本振时钟频率偏差(即符号偏差),导致解调端相位不同步,影响信号解调精度等,给出了一种改进的Gardner符号率同步方法。以经典的Gardner同步算法为基础,对插器、定时误差检测器、环路滤波器和数控振荡器进行了详细阐述,并进行了改进仿真。首先,对准基带采样信号进行插值操作,并求得插值误差;其次,对插值误差进行环路滤波(LPF)并用滤波后的信号控制数控振荡器(NCO)输出;最后,数控振荡器的输出不断更新插值点的位置,直至符号定时同步。以BPSK信号为仿真对象,仿真结果表明了改进后的符号同步算法具有更快的同步速度和更高的同步精度。

Synchronization is an essential part in digital communication systems.The transceiver uses different clock signals,but it needs to coordinate the work in a coordinated manner.It must be guaranteed by the synchronization system.The performance of the synchronization system determines the quality of the communication system in a large extent.For the receiver,there is a local oscillator clock frequency deviation (i.e.,symbol deviation),which leads to the phase of the demodulation terminal being out of synchronization,affecting the signal demodulation accuracy,etc.,thus an improved Gardner symbol rate synchronization method is presented.Based on the classic Gardner synchronization algorithm,the interpolator,timing error detector,loop filter and numerically controlled oscillator are elaborated;and improvement simulation is conducted.First,the quasi- baseband sampling signal is aligned for interpolation and the interpolation error is calculated;then,loop filtering (LPF) the interpolation error and controlling the output of the numerically controlled oscillator (NCO) with the filtered signal.Finally,the output of the numerically controlled oscillator constantly updates the position of the interpolation point until the symbol timing is synchronized.With the BPSK signal as simulation object,the simulation results show that the improved symbol synchronization algorithm has faster synchronization speed and higher synchronization accuracy.