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在无线移动通信中 ,接收机的本地振荡频率和载波频率之间往往存在较大的频率偏差 ,AFC用于克服此频偏 .传统的AFC采用了模拟环路滤波器 ,因此只能工作在连续的输入信号模式 ,而不能工作于间断导频的W CDMA系统中 .本文对此提出了新的AFC算法 :用最大似然方法估计衰落信道 ,得到间断导频信道的幅度和相位 ,并在一个时隙中进行最大比合并 ,从而得到一个判决变量 .最后用这些变量调节本地振荡频率 ,以跟踪载波频率 .仿真结果显示这种新的AFC算法是可靠而有效的 .
In wireless mobile communication, the receiver’s local oscillation frequency and carrier frequency tend to have a larger frequency deviation, AFC is used to overcome this frequency offset.Traditional AFC uses analog loop filter, it can only work in continuous Of the input signal mode, and can not work in discontinuous pilot W CDMA system.In this paper, a new AFC algorithm is proposed: the maximum likelihood method is used to estimate the fading channel to get the amplitude and phase of the discontinuous pilot channel, and in a Time slot to get a decision variable, and finally use these variables to adjust the local oscillation frequency to track the carrier frequency.The simulation results show that the new AFC algorithm is reliable and effective.