关键词: 自适应滤波, 递推最小二乘算法, 可变遗忘因子, 双曲正切函数

Abstract: In order to improve the tracking performance of the fixed forgetting factor RLS algorithm in the time-varying system，a modified RLS algorithm is proposed.The modified variable forgetting factor RLS overcomes the contravention between the tracking velocity and parameters misad-justment in the fixed forgetting factor RLS algorithm.What’s more，Kalman gain will tend to zero as the parameteresti-mates approach their true values.As a result，RLS algorithm will eventually lose its tracking ability in the time-varying system.The proposed algorithm can solve this problem.In the end，the modified RLS algorithm is simulated in the MATLAB simulation platform.The simulation results prove that this algorithm has high tracking velocity as well as high convergence velocity and small stationary error.

Key words: adaptive filtering, Recursive-Least-Square（RLS） algorithm, variable forgetting factor, hyperbolic tangent function