一种低复杂度的极低信噪比高动态信号载波粗捕获算法

 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－41 dB(载噪比C/N₀=18 dBHz)、载波多普勒频偏为－300～300 kHz、多普勒变化率为－800～800 Hz/s、码速率为20 bps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±12 Hz时,多普勒变化率精度均达±25 Hz/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%。

A Low-complexity Coarse Carrier Acquisition Algorithm for Signals with Extremely Low Signal Noise Ratio and High Dynamics

A improved carrier acquisition algorithm for signals with extremely low signal noise ratio and high dynamics is proposed. After padding extra zeroes to the signal, the algorithm shifts signal's frequency spectrum to compensate for the Doppler rate of carrier, which overcomes the high computational complexity in traditional time-domain matching-average periodogram algorithm. Its computational complexity decreases in proportion with the ratio of the number of matched branches against the quantity of zero padding, but without performance degradation. In addition, the design method of key parameters related to performance and complexity is also presented. Simulations are performed when the signal noise ratio (SNR) is -41 dB (carrier-to-noise ratio C/N₀ is 18 dBHz), Doppler frequency varies from -300 to 300 kHz, Doppler rate ranges from -800 to 800 kHz/s and data rate is 20 bps. The results show that the proposed algorithm reaches the same performance as the original algorithm does, with frequency accuracy being ±12 Hz, Doppler rate being ±25 Hz/s and acquisition probability being over 90%. The performance meets the demand of carrier tracking. The acquisition time of proposed algorithm increases by about 8% while its computational complexity decreases by 70% compared to the original algorithm.