基于卡尔曼滤波的锁频环改进算法

Improved algorithm of FLL based on Kalman filtering

为了在树荫下、建筑物内等受遮挡的环境中实现对弱信号的跟踪,需要对传统的载波环路加以改进。提出一种基于卡尔曼滤波的锁频环(frequency lock loop,FLL)改进算法,在传统FLL的鉴频器与环路滤波器中间加入卡尔曼滤波模块,并在环路滤波器和卡尔曼滤波模块之间加入数据处理模块。在相同条件下,分别对传统FLL和改进后FLL进行仿真测试。实验表明,改进后的FLL不仅能跟上信噪比低至-30dB的信号,且在跟踪精度上也比传统FLL提高很多。

The traditional carrier loop should be improved to track weak signals in shadow or in the build-ings.An improved algorithm of frequency lock loop （FLL）based on Kalman filtering is proposed for tracking weak signals.In this algorithm,Kalman filter is inserted between the discriminator and the loop filter and there is a crucial feedback circuit from the loop filter to Kalman filtering in the improved FLL.The simulation experi-ments are carried out in traditional FLL and in improved FLL with the same paremeters.Simulation results show that the improved FLL can not only successfully track signals when SNR is as low as -30 dB,but also in-crease the tracking accuracy.