符号速率采样条件下的新型复合载波跟踪环

针对低信噪比和符号速率采样条件下的载波同步问题,提出了一种新型的复合载波跟踪环,同时也给出了一种较直观的环路参数确定方法。该载波同步环改进了原有的符号硬判决算法,并通过引入采样速率变换模块使得数字锁频环(frequency-locked loop, FLL)和数字锁相环(phase-locked loop, PLL)工作在不同采样速率条件下,来提高在低信噪比环境中载波频偏和相偏的估计精度。该参数确定方法是在z域中,直接根据闭环系统的稳定性和单位阶跃响应特性来选择最优的参数。仿真结果表明,该参数确定方法具有很好的可行性,且所提出的载波跟踪环在较低信噪比条件下能获得良好的同步性能。

Novel hybrid carrier tracking loop in the case of symbol rate sampling

For carrier synchronization in the case of symbol rate sampling and low signal to noise ratios (SNRs), a novel hybrid carrier tracking loop is proposed, and an intuitive method of determining loop parameters is also investigated. The carrier synchronous loop improves the estimated accuracy of the carrier frequency offset and the phase offset in low SNR environments through modifying the original symbol hard decision method and adding sampling rate conversion blocks which enable the digital frequency-locked loop (FLL) and digital phase-locked loop (PLL) to operate under the condition of different rate sampling. The parameter determination method selects optimal parameters in the z domain directly according to the stability and unit step response characteristics of the closed-loop systems. Simulation results confirm the feasibility of this algorithm in terms of determining the parameters and indicate that the proposed carrier tracking loop achieves better synchronization performance at relatively low SNRs.