Nuttall窗改进PMF-FFT捕获算法研究

Improved PMF-FFT acquisition algorithm based on Nuttall windows

  • 摘要: 部分匹配滤波器-快速傅里叶变换(partial matched filter-fast Fourier transform,PMF-FFT)算法可实现扩频信号的快速并行捕获,然而,该算法FFT部分引入的扇贝损耗降低了信号的捕获性能.在对传统汉宁窗(Hanning window)和哈明窗(Hamming window)的扇贝损耗改善效果进行分析的基础上,针对两种窗函数由于旁瓣最大峰值和衰减速度不够理想而导致改善效果有限的不足,提出一种Nuttall窗改进的PMF-FFT信号捕获算法,选取不同项数和阶数的Nuttall窗,对其幅频特性进行分析,通过仿真实验对扇贝损耗改善效果进行验证.实验结果表明,在选取4项5阶Nuttall窗时具有较好的改善效果,可将FFT部分引入的扇贝损耗从−4.04 dB降低为−13.05 dB;在恒虚警概率下,信号的单点检测概率由20%提升至98.16%,平均捕获时间由300 ms降低为33.44 ms,有效提升了捕获性能.

     

    Abstract: The partial matched filter-fast fourier transform (PMF-FFT) algorithm can achieve fast parallel acquisition of spread spectrum signals. However, the scalloping loss introduced by its FFT part reduces signal acquisition performance. Based on an analysis of the scalloping loss improvement effects of traditional Hanning and Hamming windows, and addressing the insufficient improvement caused by their less-than-ideal maximum side-lobe peak and attenuation rate, this paper proposes a PMF-FFT signal acquisition algorithm improved by the Nuttall windows. Nuttall windows with different numbers of terms and orders were selected, and their amplitude-frequency characteristics were analyzed. Simulation experiments verified the scalloping loss improvement effect. Results show that the 4-term 5th-order Nuttall windows provides better improvement; it can reduce the scalloping loss introduced by the FFT part from −4.04 dB to −13.05 dB. Under a constant false alarm probability, the single-point detection probability of the signal increases from 20% to 98.16%, and the mean acquisition time decreases from 300 ms to 33.44 ms. This effectively improves the acquisition performance.

     

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