Research On Weak Underwater Acoustic Signals Detection Based On The Signal Coherence Properties

Signal detection is one of the important elements of the signal processing. The key pointof the Signal detection is the weak low frequency signal detection with strong noise.Thispaper introduces some classical weak signal detection methods, focusing on the weak signaldetection method based on the characteristics of the signal coherence, and proposed a newmethod called ‘coherent addition at the frequency’.This paper introduces some signal detection methods which include the classicalcopy-correlation, the power spectrogram estimation, and the LOFAR spectrogram analysis.The coherent accumulation used of the signal coherence property so that the signal formsaddition with the same phase, while the noise addition is not formed because it is random. Inwhich way we can improve the signal detection capability, But the traditional time-domaincoherent accumulation takes a long time, such as the classical adaptive coherent accumulationmethod, it needs a long time to improve the performance of weak signal detection. The newmethod called ‘coherent addition at the frequency’ proposed in this paper, can improve signaldetection capability, as well as reduce the amounts of computation.In order to make better use of the property of ‘coherent addition at the frequency’, it iscombined with ‘all-phase signal processing’ which is a new signal processing methodproposed by Wang Zhaohua and Hou Zhengxin in Tianjin University. Some introduces havebeen done for the ‘all-phase signal processing’ and all-phase FFT spectrum in this paper. Theexperiments data is analyzed at the frequency spectrum by these methods. Verify the propertyof square relation between the APFFT spectrum amplitude and the conventional FFTspectrum amplitude as well as the property of ‘phase invariant’. Through simulation andprocessing the experiments data, it is verified that the performance of weak signal detectioncan be improved by the new method. Moreover, the spectral interference also can be reducedby the combination of ‘all-phase signal processing’ and coherent addition at the frequency. Itprovides a new thought for the weak signal detection.