Postprocessing waveform selection in broadband active sonar

We discuss a technique for estimating the impulse response for an underwater acoustic signal from active sonar returns for antisubmarine warfare. This is used to study the effects of substituting one waveform for another while reducing the need for extensive at-sea data collection. This work may also form the basis for an optimization scheme whereby waveform selection is performed at the signal processing stage to maximize the signal-to-noise ratio while minimizing nonRayleigh clutter and target splitting due to over-resolution. This method is valid in the reverberation-limited regime under the assumption that there are no strong, high Doppler scatterers (clutter and targets). Our approach uses the complex matched filter time series to deconvolve a known waveform from the combined propagation and signal processing impulse response. This is done using either an analytic expression for the signal Fourier transform or a numerical, fast Fourier transform of a digitally sampled replica. Using the extracted impulse response, we may then simulate the response of an arbitrary waveform contained within the same frequency band. To validate our method, we consider band-separated, mid-frequency hull sonar data using hyperbolic frequency modulated waveforms.