Broadband source localization and signature estimation

The temporal signature and source location of a broadband impulse propagating in an ocean waveguide are estimated using matched mode processing and illustrated using simulated data in an Arctic sound channel. Matched mode processing provides a simple method for broadband signal detection and localization; the peak-to-sidelobe ratio is significantly improved using broadband data compared with the narrow-band case. The range and depth ambiguity function evaluated at the source location yields directly the source spectrum, which is inverse Fourier transformed to estimate the original signal waveform. For the simulated data, the reconstructed signal, compensated for spreading loss and array signal gain, agrees rather well with the original waveform. The estimated spectrum/waveform is weaker than the original spectrum/waveform due predominantly to the fact that the Arctic wave guide is lossy. A method for coherent broadband processing is proposed to improve signal localization and detection when the original source spectrum is known. Multiplying (correlating) the original spectrum with the range and depth ambiguity function, the product can be coherently summed over the frequency band of the signal. Near theoretical processing gain is achieved for the simulated data. Broadband signal detection is proposed using a frequency versus depth plot in addition to the commonly used frequency versus bearing plot.