改进频率鉴别的载波跟踪环路及性能分析

Carrier tracking loop based on improved frequency detector and its performance analysis

为了适应高动态环境,导航接收机常采取锁频环和锁相环联合工作实现载波跟踪。对其中较常用的的叉积自动频率跟踪环提出改进,利用两种方法切换实现频率鉴别。改进后算法克服了数据位模糊,并且使鉴频范围扩大了4倍,同时保持跟踪精度不变。影响跟踪精度的因素主要包括热噪声误差和动态应力误差,经研究发现其中热噪声误差的传统理论分析结果与实际有较大差距。利用环路线性化近似处理,并且考虑鉴别噪声间的相关性,经重新推导得到锁频环路的热噪声跟踪误差低于传统理论分析结果的1/5。通过仿真对锁频环鉴频范围和热噪声跟踪误差分析的正确性进行了验证。

To meet the high dynamic environment, global navigation satellite system receivers often combine frequency-locked loop with phase-locked loop to track carrier. An improvement on cross-product automatic frequency control loop, which is commonly used, is proposed. The new loop adopts the switch between two identification methods. As a result, it can overcome the data ambiguity and expand the frequency discrimination range 4 times while maintaining the same tracking accuracy. The main factors affecting the tracking accuracy include noise tracking error and dynamic stress error. It is found that there is a greater gap between the traditional theory of thermal noise error and actual results. Using loop linear approximation and considering the relevance of noises in identification results, the new thermal noise tracking error equation is derived. The new value is less than one-fifth of traditional theoretical analysis. Finally, the analysis of frequency discrimination range and thermal noise tracking error is proved by simulation results.