适用于相位调制的改进恒模算法

A Modified Constant Modulus Equalization Algorithm Applicable to Phase Modulation

恒模算法(CAM)实现盲均衡直接利用接收信号本身的先验信息对信道进行均衡,避免采用"训练序列",提高了有效信息率。但该算法也存在着不足之处。对于MPSK、MQAM等相位调制方式来说,在相位偏转信道中散点图存在相位偏转;与带有"训练序列"的均衡模式相比该算法输出信号均方误差大,收敛速度慢。改进的算法通过在代价函数中加入相位信息,较好解决了散点图相位偏转问题;将输出信号判决值引入误差计算装置,有效降低了输出信号的均方误差,并在一定程度上提高了收敛速度。

Constant Modulus Equalization Algorithm（CMA） realizing blind equalization directly equalizes the received signal by means of its priori information, thus advoiding the use of training sequences and improving the effective information rate. However, this algorithm also has some disadvantages. For MPSK and MQAM, the scatter diagram has excursion in phase excursion channel, as compared with the equalization algorithm with ＂training sequence＂, this algorithm has fairly large MSE of output signaland relatively low convergence rate. The improved algorithm, by adding phase information to the cost function, could has a better solution to the problem of scatter diagram phase excursion. By introducing the decision value of output signal into the error calculation device, the MSE of output signal could be effectively reduced and the convergence rate of output signal raised to a certain extent.