Experimental Measurement of the Near-Fields of a UHF Horn Antenna

The purpose of this report is to determine quantitatively some of the practical limitations of testing in the near field of UHF horns; in particular, how near to the horn aperture is the field reasonably uniform in amplitude and phase for a given size test object. This report describes in detail near field measurements of both the electric (E) and magnetic (H) vectors from the aperture of a UHF horn out to a distance of 4.8 meters. These measurements encompass a rectangular volume of dimensions 2.4m x 3m x 4.8m. The data spatial separation (i.e., spatial resolution) is 0.1m in each orthogonal direction. The E and H field data is analyzed and displayed graphically. It is analyzed independently and combined to show the wave impedance behavior in the near zone. By observation of the data presented, one can immediately develop engineering guidelines for defining the useful test volume in the near zone of a UHF horn. (Author). Appendices include MICOM report, DRSMI/RT-80-9-TR, IEEE papers from the Proceedings of IEEE Southeastcon 1981: Design, Construction, and Calibration of Pseudo-Transparent Non-Interfering Electric and Magnetic Field Sensors, by Brian Strickland, G. R. Edlin and T. H. Shumpert; Experimental Determination of the Near-Zone of a High Power UHF Horn Antenna, by T. H. Shumpert, T. A. Blalock and G. R. Edlin.