An Empirical Near-Field to Far-Field Convergence Study for Antenna Measurements
Paul J. Nelson, Justin Henrie
Naval Air Warfare Center Weapons Division
Pattern distortion due to finite range measurement of antennas in close proximity to electrically large metallic media is examined. The ubiquitous yet arbitrary 2D^2/lambda distance requirement cannot be blindly applied to scenarios where antennas couple to nearby structures. A C-band standard gain horn antenna is analyzed near a circular metallic plate at 6 GHz using the commercial software FEKO. The near-fields are computed at various radii, which are set to multiples of D^2/lambda, where D is defined as the largest dimension of the complete structure. The radiating near-field patterns are normalized and compared to the far-field pattern. Results indicate that measurement at 2D^2/lambda may not be necessary. Increasing fractions of D^2/lambda results in a diminishing measurement error that may be tolerable, depending on the intended application.
Proc. AMTA
2011
October
464-468
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