Adaptive and synthetic aperture processing structures for high-resolution mine-hunting sonars deploying planar or cylindrical arrays

The developments reported in this paper have been devoted to minimizing the influence of partially directional noise fields as well as maximizing the array gain of mine-hunting sonar systems by means of signal processing. The effort of this study included the design of a generic beamforming structure that allows the implementation of nonconventional signal-processing techniques in integrated active/passive sonar systems. The nonconventional processing schemes of this study are adaptive and synthetic aperture beamformers that have been shown experimentally to provide improvements in array gain for signals embedded in partially correlated noise fields. The reported results show that synthetic aperture and adaptive processing schemes with near-instantaneous convergence can be implemented in mine-hunting sonars deploying 3D arrays. Moreover, practically realizable angular resolution improvements provided by the nonconventional beamformers are equivalent with those provided by the conventional beamformer of a three-times-longer physical aperture and for broadband FM type of signals. The same set of results demonstrates also that the combined implementation of a synthetic aperture and the subperture STMV adaptive scheme suppresses significantly the sidelobe structure of cw pulses for mine-hunting operations. In summary, the present paper attempts to address characterization of source signals detected by planar or cylindrical arrays of mine-hunting sonar systems with 3D image resolution capabilities.