Detection of weak signal with low Doppler frequency in waveguide

A combined system for Doppler detection in waveguide is proposed to detect weak signals with low Doppler. A method based on adaptive noise cancelling methods using the autoregressive moving average (ARMA) was proposed to cancel the reverberation adaptively. Compared with the adaptive notch (AN) filter, it is not necessary to know the frequency of reverberation. A normalization method based on fluctuant frequency feature which was combined with frequency variance and kurtosis in frequency domain was presented to fulfill constant false alarm ratio detection. Before the constant false alarm rate (CFAR) method, making use of the echo time dispersion in shallow water, mean processing between two snap-shots was used to detect continuous wave (CW) in a multipath. The results show that frequency response of stopband filter about adaptive reverberation notch using autoregressive model (ARNAR) is better than that of AN, and the bandwidth of stopband about ARNAR is not controlled by the adaptive coefficient. The simulation experiments on detection of low Doppler signals in strong reverberation noises show that the system is effective.