摘要
主动声纳探测水下目标时,目标散射特性以及水声传播特性会对接收回波产生影响。针对水中沉底与掩埋目标探测时存在的混响干扰强、信混比低等问题,本文提出了一种基于分数阶傅里叶变换(Fractional Fourier Transform,FRFT)的变频Duffing振子检测方法。在发射LFM信号探测水下目标时,目标回波信号为多个LFM信号线性叠加的形式,不符合Duffing振子的单频检测条件。基于FRFT理论,提出了在最佳FRFT域上对LFM回波信号进行傅里叶逆变换的解调频方法。并根据亮点模型,推导了多亮点LFM回波信号解调频后的信号形式。由理论分析可知,解调频后的单频信号数量与亮点数量一致,频率大小与亮点时延及发射信号参数有关,为未知参量。针对解调频后频率及数量未知这一问题,提出了变频Duffing振子系统检测模型,通过改变系统内置策动力频率,自主地搜索单频信号信息,实现了低信混比下LFM目标回波信号的检测及亮点数量的估计。湖试沉底及海试掩埋实验数据处理结果验证了方法的有效性及可行性。
Aiming at influence of target scattering characteristics and underwater acoustic propagation char⁃acteristics on sonar receiving echo in the detection of water and sink buried objects where the reverberation and low signal mixing ratio exist,a variable-frequency detection method of Duffing oscillator based on FRFT is proposed.When LFM signal is transmitted to detect underwater targets,the target echo signal is linear su⁃perposition of multiple LFM signals,which does not meet the single frequency condition of the Duffing oscil⁃lator.Based on fractional Fourier transform theory,the method of frequency modulation in the optimal FRFT domain is proposed.According to the bright spot model,the signal form after demodulation of multiple brightpoints LFM echo signal is deduced.The analysis shows that the number of single frequency signals after de⁃modulation is consistent with that of bright points,and the frequency is related to the highlight delay and the transmitted parameters of the signal,which are unknown parameters.For the above problem,a variable fre⁃quency detection model of Duffing oscillator systems is proposed.The single-frequency signal is detected au⁃tonomously by changing the frequency of the driving force,and the detection of LFM target echo signal and the number estimation of bright spots under low signal mixing ratio are realized.The data processing results of the lake and sea trials show the effectiveness and feasibility of this method.
作者
李楠
杨阳
LI Nan;YANG Yang(College of Information Engineering,Northeast Electric Power University,Jilin 132012,China;College of Information Engineering,Dalian University,Dalian 116622,China)
出处
《船舶力学》
EI
CSCD
北大核心
2021年第5期670-680,共11页
Journal of Ship Mechanics
基金
国家自然科学基金资助项目(61901079)。
