Matched-mode processing schemes of a moving point source

Abstract

Matched-mode processing schemes are presented to estimate the frequency, velocity, depth, and range information of a time-harmonic point source moving uniformly in a stratified oceanic waveguides. When the velocity of a moving source is much smaller than the sound velocity of the waveguide, the acoustic field generated by this moving source can be represented in terms of normal modes with different Doppler-shifted frequencies and, hence, different changes of modal eigenvalues. The shifted frequencies of each mode can be derived by the conventional approach for the Doppler effect in an unbounded medium with the corresponding modal phase velocity as the equivalent sound velocity of the medium. Then, the shifted modal eigenvalue is obtained by solving the transverse resonance equation of the waveguide. The frequency information alone is good enough to estimate the source velocity and frequency (unshifted), but the eigenvalue information has to be included to estimate the source depth and range. Processing schemes over the time domain (using a single receiver) and that over both space and time domains (using a vertical receiving array) are discussed in details with emphasis on deriving practical criteria of choosing processing parameters. These criteria are good for both shallow and deep oceans with arbitrarily stratified sound profiles.