Subspace Detector of Multi-Frequency Signals Using the Single Hydrophone in Bottom Bounce Zone

Passive source detection is challenging in underwater acoustic signal processing. In this work, we consider the passive source detection using a single hydrophone in the Bottom Bounce (BB) zone in deep water. No prior knowledge about the ocean environment is assumed available, rendering the matched-field processing method to be unachievable. In this case, the classical Energy Detector (ED) can be used. It incoherently superimposes the energy of multi-frequency signals and declares the presence or absence of the source by comparing the signal energy to a prescribed detection threshold. While the ED's performance is highly limited by the low signal-to-noise phenomenon in this zone. This paper proposes a subspace detector that coherently accumulates the multi-frequency signals energy by exploiting the multipath arrival structure characteristics of BB signal. The detector realizes coherent accumulation of multi-frequency signals by projecting the signals into the proposed vector subspace, thus rejecting noises outside the subspace and improving the detection performance. The performance superiority of the proposed detector over ED is verified by simulation in a typical deep-water channel.