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针对传统的时域匹配平均周期图算法计算复杂度高的问题,对极低信噪比高动态信号的载波粗捕获算法进行了研究,提出了一种改进的带有补零的频域移位平均周期图算法。该算法采用多速率频域移位运算简化了多支路多普勒变化率匹配,与原算法相比,其计算复杂度降低倍数为匹配支路数与补零倍数之比,捕获性能几乎不损失。给出了算法中影响捕获性能与计算复杂度的关键参数设计方法。在信噪比(SNR)为-41dB(载噪比C/N0=18dBHz)、载波多普勒频偏为-300～300kHz、多普勒变化率为-800～800Hz/s、码速率为20bps条件下对两种算法进行了仿真,结果表明在基本满足后级载波跟踪需求条件下,即频偏精度均达±12Hz时,多普勒变化率精度均达±25Hz/s,捕获概率都在90%以上时,改进算法捕获时间比原算法增加了8%,计算复杂度降低了70%。
Aiming at the problem of high computational complexity of the traditional time-domain matching averaging periodogram algorithm, a coarse-hull carrier acquisition algorithm with very low signal-to-noise ratio and high dynamic signal is studied. An improved frequency-domain shift with zero-padding Average Periodogram algorithm. Compared with the original algorithm, the algorithm reduces the computational complexity by the ratio of the number of matched branches to the multiple of the zero-filling multiple, and the acquisition performance is almost no loss. The design method of key parameters affecting the acquisition performance and computational complexity is given. The SNR is -41dB (carrier to noise ratio C / N0 = 18dBHz), the carrier Doppler frequency offset is -300 ~ 300kHz, the Doppler rate of change is -800 ~ 800Hz / s and the code rate is 20bps The results show that the precision of Doppler rate of change is up to ± 25Hz / s when the frequency offset accuracy reaches ± 12Hz, and the acquisition probability is When more than 90%, the improved algorithm capture time is increased by 8% and the computational complexity is reduced by 70%.