Abstract
The primary difference between phased-array sonar and acoustical holography lies only in the order in which the temporal and spatial processing operations are carried out. It is shown that this difference indirectly leads to an advantage for holography in terms of either signal-tonoise performance or reduced processing complexity in many types of application. The holographic approach has an important signal-to-noise advantage over scanned phasedarray systems because of parallel processing. Compared with multibeam sonar, the holographic spatial processing of data obtained from uniform arrays can be carried out with fewer operations than phased-array parallel beam-forming via adders and tapped shift registers because of the CooleyTukey algorithm. A significant reduction in processing operations due to data reduction in holography, especially for active systems, is also possible.
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References
See, for example, H. G. Frey, “High Resolutions Sonar Technology,” Vol. II, p. 43, Classified Report No. 69-R-NRC:MAC:2027.
See, for example, H. R. Farrah, E. Marom, and R. K. Mueller, p. 173, Acoustical Holography, Vol. 2, Ed. by A. F. Metherell and L. Larmore (Springer Science+Business Media New York, 1970); R. K. Mueller, Proc. IEEE, 59, 1319 (1971).
For the purposes of this discussion, we define phasedarray systems as those in which the spatial processing (e.g., beam-forming) is carried out before the temporal processing, and holographic systems as those in which the reverse is true, the reconstruction being carried out last.
See, for example, P. N. Keating, R. F. Koppelmann, R. K. Mueller, and R. F. Steinberg (to be published).
M. O. Fein and E. S. Eby, Naval Underwater Sound Laboratory Technical Memo No. 2242–173–69 (July 1969).
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In actual fact, the original DIMUS approach used only one-bit words whereas current holographic systems use 8–12 bits for each word. However, one-bit words can be used for holography [see, for example, W. J. Dallas and A. W. Lohmann, Acoustical Holography, Vol. 4, p. 463, Ed., G. Wade (Springer Science+Business Media New York, 1972)] with the same drop in performance as in DIMUS. Alternatively, a comparison with current holographic systems should involve an “improved” DIMUS with 8–12 bit digitization and the corresponding reduction in quantization “noise”.
J. W. Cooley and J. W. Tukey, Math. Comput., 19, 297 (1965).
B. Gold and C. M. Rader, Digital Processing of Signals (McGraw-Hill, New York, 1969).
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© 1974 Springer Science+Business Media New York
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Keating, P.N. (1974). Acoustical Holography — A Comparison with Phased Array Sonar. In: Green, P.S. (eds) Acoustical Holography. Springer, Boston, MA. https://doi.org/10.1007/978-1-4757-0827-1_14
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DOI: https://doi.org/10.1007/978-1-4757-0827-1_14
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