摘要
针对大多普勒频偏、低信噪比条件下长周期伪码的扩频信号捕获问题,提出了一种基于圆周相关扩频信号的快速捕获改进方法。该算法对圆周相关后的结果利用快速傅里叶变换(FFT)进行频率估计,扩大了传统圆周相关法的扫频步进,使扫频步进不再受跟踪环路带宽的限制。理论分析及仿真结果表明,在信噪比为-34 dB、多普勒频率为500 kHz条件下算法可以正确地估计出伪码相位和多普勒频偏。在达到相同的灵敏度条件下,所提算法的平均捕获时间与传统的圆周相关法相比缩短了约47%,与基于FFT的并行频率搜索法相比缩短了约88%。另外,用于频率估计的FFT点数仅占圆周相关点数的1%,故额外增加的硬件资源很少。算法逻辑控制简单,尤其适用于大多普勒频偏、低信噪比及长周期伪码的卫星通信系统。
Aiming at the problem of spread spectrum signal acquisition with long period pseudo-noise(PN)code under the condition of high Doppler frequency and low signal-to-noise ratio,an improved algorithm based on circular correlation for fast acquisition of spread spectrum signals was proposed.Since the algorithm used fast Fourier transform(FFT)to estimate the frequency offset of the results obtained by circular correlation and expanded the frequency sweep step of the traditional circular correlation method,the frequency sweep step was no longer limited by the tracking loop bandwidth.The theoretical analysis and simulation results indicate that the algorithm can correctly estimate the PN code phase and Doppler frequency under the signal-to-noise ratio of-34dB when the Doppler frequency is 500kHz.With the same sensitivity,the mean acquisition time of the proposed algorithm is shortened by about 47%in comparison to the traditional circular correlation algorithm,and about 88%in comparison to the FFT-based parallel frequency search algorithm.In addition,the FFT points used for frequency estimation only account for 1%of the circular correlation points.The algorithm is proved to be a straightforward logic-controlling solution,which can significantly increase the real-time performance of the satellite communication system with a high Doppler frequency,low signal-to-noise ratio,and long period PN code.
作者
刘洁
张朝杰
金小军
金仲和
LIU Jie;ZHANG Chaojie;JIN Xiaojun;JIN Zhonghe(School of Aeronautics and Astronautics,Zhejiang University,Hangzhou 310027,China;Key Laboratory of Micro-nano Satellite Research,Hangzhou 310027,China)
出处
《中国空间科学技术（中英文）》
CSCD
北大核心
2024年第2期109-117,共9页
Chinese Space Science and Technology
基金
国家自然科学基金(62073289)。
关键词
卫星通信系统
直接序列扩频
信号捕获
圆周相关
快速傅里叶变换
satellite communication system
direct sequence spread spectrum
signal acquisition
circular correlation
fast Fourier transform
