一种用于星间相干激光通信的频偏估计算法

A Frequency Offset Estimation Algorithm for Inter-Satellite Coherent Laser Communication

载波频偏估计算法是星间相干激光通信系统解调算法的重要组成部分,算法性能直接决定后续判决的精度,对整个系统的通信性能起到了至关重要的作用。文章提出了一种基于快速傅里叶变换(FFT)和频谱细化方法相结合的两级频偏估计算法,利用星载设备较少的计算资源,实现了载波频偏粗估计和精细估计的高精度联合估计。仿真结果表明,当两级FFT点数分别为128和2048时,算法的信噪比阈值为8dB,当信噪比大于阈值时,算法的估计精度与基于FFT的频偏估计算法相当,归一化频率方差达到10^(-10),优于基于相位增量的频偏估计算法。此时,相较于基于FFT的频偏估计算法,本文所提算法的实数乘法和加法次数分别减少了25.17%和55.19%,因此算法复杂度大大降低。

The carrier frequency offset estimation algorithm is an important component of the demodulation algorithm for inter-satellite coherent laser communication systems.The algorithm performance directly determines the accuracy of subsequent judgments and plays a crucial role in the communication performance of the cntire system.This article proposes a two-stage frequcn-cy offset estimation algorithm based on a combination of Fast Fourier Transform(FFT)and spec-tral zoom methods,which utilizes the limited computational resources of onboard devices to a-chieve high-precision joint estimation of carrier frequcncy offset coarse estimation and fine esti-mation.The simulation results show that when the number of FFT points in two levels is 128 and 2048,the signal-to-noise ratio threshold of the algorithm is 8dB.When the signal-to-noise ratio is greater than this threshold,the estimation accuracy of the algorithm is equivalent to that of the FFT based frcqucncy offset estimation algorithm,with a normalized frcqucncy variancc of 10^(-10),which is superior to the phase increment based frequency offset estimation algorithm.At this moment,compared to the frequency offset estimation algorithm based on FFT,the real number multiplication and addition times of the algorithm proposed in this article have been re-duced by 25.17%and 55.19%,respectively,the algorithm complexity has bcen grcatly rc-duced.