基于FFT和相干累积的DS/FH测控信号捕获算法

对于某种相干跳频和直接序列扩频结合的抗干扰测控信号,捕获时存在码相位快速搜索和大时差大多普勒条件下相干累积的问题。本文采用基于FFT并行相关的分段码相关算法,实现积分时长为单个跳频段的快速码相位滑动相关；采用相位补偿算法,补偿各个跳频段间因时间差、跳频频率和多普勒导致的相位差,实现了较大多普勒频偏条件下跳频段之间的相干累加。分析了相位补偿算法的累积损耗和时间复杂度,仿真试验证实了检测性能。与非相干累加相比,本算法消除了大时差大多普勒条件对信号长时间相干累积的影响,在某信号体制下检测性能提升9dB左右,代价是算法复杂度随捕获时间分辨率的增加而线性增加。

FFT-and-Coherent-Accumulation-based Acquisition of DSFH TT C Signal

In the acquisition of a hybrid direct-sequence and fast-frequency-hopping(DSFH) spread spectrum signal, the fast scanning of unknown time delay and the coherent accumulation under large Doppler are two main obstacles. In our algorithm, an FFT-based code correlator performs the fast slide-correlation in each hop, a phase-compensation-based accumulator compensates the phase errors between different hops and performs the coherent accumulation among several hops under large Doppler frequency. The signal-to-noise ratio loss and the complexity of this algorithm are analyzed and simulations verify the detection performance. Comparing to non-coherent accumulation, this algorithm improves the detection performance by 9dB at the expense of a linear increase of computation complexity.