解调带宽对船舶辐射噪声调制谱的影响

利用傅里叶分解原理建立了幅度调制的船舶辐射宽带噪声信号数学模型,导出了基于平方解调算法船舶辐射噪声调制谱数学表达式。通过理论分析和仿真计算得到了关于调制谱分析两个新的结论:(1)解调性能与解调处理带宽关系:在声呐接收的船舶辐射噪声各频带调制度相同时,解调性能正比于解调所采用的带通滤波带宽,解调所采用的带通滤波带宽越宽,解调谱信噪比越高;(2)宽带解调谱和子频带解调谱之间关系:船舶辐射噪声宽带解调谱可以近似认为各子频带解调谱之和。为了验证以上两点结论,对实际船舶辐射噪声解调谱进行了相应处理,结果与仿真计算吻合较好。

The Influence of demodulation bandwidth on modulation spectrum of ship-radiated noise

A mathematical model of amplitude-modulated ship-radiated broad-band noise signal is established based on the principle of Fourier Decomposition, deriving a mathematical expression for modulation spectrum of the ship-radiated noise based on the square demodulation algorithm. Two new conclusions from analysis of the modulation spectrum are obtained based on theoretical analysis and simulation calculation: (1) relationship between demodulation performance and demodulation processing bandwidth: when the modulation depths of different frequency bands of ship-radiated noises received by a sonar are the same, the demodulation performance is positively proportional to bandwidth of the band-pass filter used for demodulation; the wider the band-pass filter bandwidth is, the higher the signal-to-noise (SNR) ratio of the demodulation spectrum is; (2) relationship between broadband demodulation spectrum and sub-band demodulation spectrum: the broadband demodulation spectrum of the ship-radiated noise can be approximately regarded as a sum of different sub-band demodulation spectrums. To verify the two conclusions above, the actual demodulation spectrum of the ship-radiated noise is processed correspondingly, showing that the result is consistent with the result from simulation calculation.