This paper presents an algorithmto observe frequency deviation （FD） for QAM signal reception.It can be used in an all degital receiver where the synchronizer no longer employs any PLL.This paper first presents the algorithm of the FD observer

and then introduces 1st order FD Kalman filtering algorithm

at last combines the FD observer and thd FD Kalman filter to form an FD estimator

which provides a practical solution for carrier synchronization in mobile communication channel.