多径CD3S信号的混合卡尔曼滤波解调

Demodulation of CD3S signals through mixed Kalman filtering for multipath channel

提出了一种基于混合卡尔曼滤波的CD3S信号解调算法,在多径衰落信道下,采用状态估计的方法解调混沌直接序列扩频（CD3S）信号.根据混沌系统映射方程建立了混沌码同步问题的状态空间模型,并利用无损卡尔曼滤波器实现了混沌码同步;根据信道参数与信息码相对于混沌码的慢变特性,建立了信道参数估计与信息码估计问题的状态空间模型,并利用两个卡尔曼滤波器分别估计信道参数与信息码.三个滤波器均把彼此的估计结果作为系统参数,交替工作,通过联合估计实现信息码解调.仿真结果表明：无论多径信道是时不变的还是时变的,算法均可以提高混沌码同步精度,降低CD3S通信系统误码率.

A demodulation algorithm for CD3 S signals was proposed based on the mixed Kalman filter（KF）,and the chaotic direct sequence spread spectrum（CD3 S） signals were demodulated by state estimation in multipath fading channel.The state space model of chaotic code synchronization was established based on chaotic map,and chaotic code synchronization was realized by unscented Kalman filter（UKF）.According to the slow-varying of channel parameter and data symbol compared with chaotic code,the state space models of channel parameter estimation and data symbol estimation were established,and two Kalman filters were used to estimate channel parameters and information data symbol respectively.The three filters respectively used each another＇s estimation results as the system parameters and worked alternately to accomplish demodulation by joint estimation.Simulation results demonstrate that the algorithm can improve the chaotic code synchronization accuracy and reduce CD3 S communication system＇s bit error rate,no matter whether the channel is time invariant or time-varying.