From matched filter to matched field tracking

An old example of use of a matched filter in underwater sound is the quadrature detector. The signal from hydrophone ♯j is split, and one channel is matched with a cosine wave and the other with a sine wave. These channels are assembled as the real and imaginary parts of the analytic signal Fj. The next application of a matched filter occurs in plane wave beam forming where the signals {Fj} of an array are matched with signals {Gj(φ)}, which are expected if the incident signal is a plane wave with direction φ. The problem is expanded when a more precise form of {Gj} is used. In general, {G} will be a function of the location of the source. Therefore, in principle, the location of a sound source can be found by finding the coordinates of the best match between the F’s and the G’s (matched field processing). Several methods will be described showing how to do this in an efficient manner. Finally, there is further gain to be had by including many time values in matching the track of the acoustic source (matched field tracking). Examples will be shown illustrating results from sea tests.