| Abstract: | This article describes a digital implementation of time-delay sonar imaging for linear swept-frequency (chirp) sources. The technique, based on phase-shifting of match-filtered individual transducer echoes, is a direct equivalent of analog phased-array processing. Computing and sampling costs are minimized by sparse population of the receiver aperture, using a separate transmission array with controlled beamwidth to suppress grating lobes. Synthetic-aperture processing uses essentially the same computation, and is carried out for a chirp signal without frequency decomposition. When different arrays are used for transmission and reception, azimuthal resolution depends on transmission array length, but maximum movement between pings without aliasing is set by the length of the receiver array, so high resolution is compatible with fast survey. This article describes how a closely related algorithm can be used for swath bathymetric depth estimation, and presents simulation results using a random surface scatterer model. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 359–376, 1997 |
