连续波主动声呐低截获概率波形设计及目标检测算法的研究

Continuous active sonar (CAS) has advantages of high processing gain and fast update rate of target information, which is particularly suitable for detection and tracking of underwater quiet targets and fast moving targets. Waveforms with low intercept probability and algorithms of echoes detection for CAS will be deeply researched, with the background of shore based sonar. Orthogonal signals combinations composed of frequency hopping waveforms and pseudo random codes modulation waveforms are proposed, which can improve performances of anti-interference and anti-interception for continuous waveforms. Constant envelope waveforms designed by pseudo random sequences frequency modulation and continuous phase modulation are proposed to improve peak to average ratio of sequences modulated waveforms. Constrained nonlinear programming will be applied to optimize pulse compression performance and orthogonality of sequences modulated waveforms, after mathematical model is established. In order to improve the processing gain and target information update rate, a unified signal processing framework is established, which can detect orthogonal signals, using multi-channel parallel processing and non-coherent processing. Space-time signal processing will be applied for suppression of direct arrival interference and continuous reverberation, after simulation model of continuous reverberation is designed. A test system will be built to verify the performance of the proposed waveforms and algorithms, and statistical characteristics of continuous reverberation will be analyzed. Researches on key scientific problems of CAS, not only can provide theoretical basis for its engineering application, but also promote the development of marine detection equipment and coastal defense.

连续波主动声呐具有处理增益高、目标信息更新快的特点，特别适合水下安静目标和快速运动目标的探测和跟踪。课题以岸基声呐为研究背景，对连续波主动声呐的低截获概率波形和回波检测算法进行深入研究。设计跳频波形和伪随机编码调制波形构成的正交子信号组合，提高连续波形的抗干扰和抗截获性能。设计伪随机序列调频和伪随机连续调相恒包络波形，改善编码调制波形的峰均比。建立数学模型，使用带约束的非线性规范方法优化伪随机序列调制波形的脉压性能和正交性能。建立统一的信号处理框架，基于多通道并行处理和非相干处理对正交子信号进行回波检测，用于提高处理增益和目标信息更新率。建立连续混响的仿真模型，利用空域和时域二维信号处理抑制直达波干扰和连续混响。搭建试验系统，验证波形和算法的性能，分析连续混响的统计特性。对连续波声呐关键科学问题的研究，为其工程应用提供理论依据，并推动海洋探测装备和近海防御技术发展。

主动声呐是水面舰船和水下航行器主要的水下信息获取方式，是各国海军进行水下监视和警戒使用的主要技术。目前的主动声呐，均为脉冲式主动声呐(Pulsed Active Sonar, PAS)，脉冲重复间隔较大，限制其探测性能。与PAS相比，连续波主动声呐(Continuous active sonar)持续发射波形，具有很多优势：信号处理增益高，扩展声呐的探测范围；目标信息更新快，提高目标跟踪稳定性；降低突发短时干扰的影响等。CAS的研究完善我国主动声呐体系，增强水下防御能力。. 本项目在CAS探测波形设计和回波检测算法等方面开展研究。本项目设计了跳频-线性调频(FH-LFM)波形，建立了水下回波模型，设计了多通道正交解调-匹配滤波和非相干累加的处理方式。这种统一的信号处理框架，一方面提高处理增益，另一方面提高目标信息更新率。对于20个子脉冲的连续波形，目标信息更新率可达到1秒左右，检测性能比PAS提高9-10dB。此外，使用遗传算法设计了正交的MSK波形，该信号具有良好的自相关性(脉冲压缩性)和正交性。使用凸优化设计波束图，并通过实测阵列的阵列流形，防止阵列误差的影响。借助接收机工作特性曲线，分析了CAS探测性能，并与PAS比较，为CAS设计和性能评估提供一种方法。解决了线性调频连续波多目标检测问题，避免了强目标对弱目标检测和估计的影响。项目组搭建试验系统，开展水下试验。设计了一款全数字式声呐发射机，改进了功率放大器的控制方式降低了声呐复杂度和调试难度，提高了系统的可靠性。