Noise normalization of broadband sonar data in bearing space

Detection of broadband signals is difficult in the sonar application due to the uncertainty in the broadband noise power and hence the uncertainty in the threshold required for detection. However, if the receiver has sufficient directivity, then it is possible to exploit the spatial characteristics of the broadband field to isolate plane wave signals from the more diffuse noise background. This paper considers a parameterization of the broadband bearing estimate from a line array receiver in terms of complex modes (Prony method). Identification of the modes associated with the plane wave arrivals is examined as a means of directly separating the signals from the noise. Only broadband beampowers are assumed available, so the bearing estimates are contaminated by the array response. Issues of mode number and estimation error are addressed by way of example.