基于FFT实现短波扩频系统载波频差估计

短波扩频系统中，由于伪码速率低，加上频率源不稳定及多普勒频移的影响，收发端载波往往存在一定频差，使得PN码无法同步。针对这种情况，提出了对正交下变频后I，Q两路信号相乘的结果做快速傅立叶变换来估计频差的方法。这种方法简单易行，且不受PN是否同步的影响，可以把收发端载波频差控制在很小的范围内。

Estimation of the Carrier Frequency Difference of HF Spread Spectrum System Based on FFT

In HF spread spectrum system, because of the low rate of pseudo code, coupled with instability of the frequency source and the Doppler frequency shift, some frequency difference is often exit there between the carrier of transceiver and receiver, the frequency difference makes the PN code failed to establish synchronization. In response to this situation, an approach is presented to estimate the frequency difference based on Fast Fourier Transform to the multiplication of in-phase and quadrature signal. This method is easy to realized, and is not affected by PN code synchronization or not, it can control the frequency difference in a small range.