Spatial Sampling Criteria for Nearfield Measurements Made on Cylindrical Surfaces,
ADMIRALTY UNDERWATER WEAPONS ESTABLISHMENT PORTLAND (ENGLAND)
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This report establishes the spatial sampling criteria for nearfield measurements, made on a cylindrical surface enclosing the sources, that enable the farfield of those sources to be calculated faithfully from the nearfield data. Examples are given of the criterial applied to both omnidirectional and directional sources their nearfield and calculated farfield. The sampling criteria for nearfield measurements made on a cylindrical surface have been established in this report for both axial and circumferential samples. In general the common practice of using half wave length samples circumferentially is shown to be adequate for omnidirectional field narrow spatial bandwidths but not adequate for the broad circumferential spatial bandwidth fields encountered with directional sources.