基于FFT和长时延自相关函数的频偏估计方法

Carrier frequency offset estimation algorithm based on FFT and long delay autocorrelation function

为了解决低信噪比条件下载波频偏估计中的估计范围和估计精度的矛盾,在比较分析现有经典估计方法的基础上,提出一种基于FFT和长时延自相关函数的频偏估计方法。该方法利用FFT进行粗略频偏估计以校正频偏,使得校正后的频偏落入到长时延自相关函数能够估计的频偏范围内,利用几个长时延函数得到的剩余频偏估计值进行加权得到精确的频偏估计值。此方法将频偏估计范围提高到数据速率的一半,保证了在大频偏时的低信噪比门限,同时它在整个量化频率范围内的性能平稳。通过仿真验证了该方法估计精度高、捕获范围大、以及性能平稳的特点。

In order to solve the problem of the contradiction between capturing range and estimation accuracy of frequency offset estimation methods for low signal to noise ration （SNR） condition, an new carrier frequency offset estimation algorithm based on FFT and long delay autocorrelation function is proposed. The new algorithm uses estimated frequency offset obtained by FFT to adjust frequency offset, so the remainder frequency offset is in the range of frequency offset that the long delay autocorrelation function can handle. Accurate frequency offset estimation is obtained by calculating the weighted sum of the rough estimation which is obtained from several long delay autocorrelation function. It extends its estimation range to a half data rate, at the meantime, its SNR threshold is low at small SNR, the frequency estimation capacity in the whole frequency range is steady. The simulations illustrate the algorithm performance of high estimation accuracy, wide capturing range and steady capacity.