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Proceedings Paper

Phase measurements of electromagnetic fields using infrared imaging techniques and microwave holography
Author(s): John E. Will; John D. Norgard; Carl Stubenrauch; Katie MacReynolds; Michael F. Seifert; Ronald M. Sega
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Paper Abstract

Complex (magnitude and phase) measurements of the near field of a radiating antenna over a known surface (usually a plane, cylinder, or sphere) can be used to determine its far-field radiation pattern using near-field to far-field Fourier transformations. Standard gain horn antennas are often used to probe the near field. Experimental errors are introduced into the near-field measurements by mechanical probe position inaccuracies and electrical probe interactions with the antenna under test and probe correction errors. A minimally perturbing infrared (IR) imaging technique can be used to map the near fields of the antenna. This measurement technique is much simpler and easier to use than the probe method and eliminates probe position errors and probe correction errors. Current IR imaging techniques, which have been successfully used to rapidly map the relative magnitude of a radiating field at many locations (mXn camera pixels per image captured) over a surface, however, suffer from an inability to determine phase information. Absolute magnitude and relative phase data can be obtained by empirical or theoretical calibration of the IR detector screens (used to absorb the radiated energy over the measurement plane) and by using techniques from microwave holography. For example, magnitude only measurements of the radiating field of an antenna at two different locations (over two different surfaces) in the near field of the antenna can be used to determine its complex (magnitude and phase) far-field radiation pattern using plane-to- plane (PTP) iterative transformations. This paper discusses the progress made to data in determining both magnitude and phase information from IR imaging data (IR thermograms); thus, enabling near-field and far-field measurements of antenna patterns using IR thermal imaging techniques.

Paper Details

Date Published: 15 March 1996
PDF: 11 pages
Proc. SPIE 2766, Thermosense XVIII: An International Conference on Thermal Sensing and Imaging Diagnostic Applications, (15 March 1996); doi: 10.1117/12.235388
Show Author Affiliations
John E. Will, Univ. of Colorado/Colorado Springs (United States)
John D. Norgard, Univ. of Colorado/Colorado Springs (United States)
Carl Stubenrauch, National Institute of Standards and Technology (United States)
Katie MacReynolds, National Institute of Standards and Technology (United States)
Michael F. Seifert, Rome Lab. (United States)
Ronald M. Sega, NASA Johnson Space Ctr. (United States)

Published in SPIE Proceedings Vol. 2766:
Thermosense XVIII: An International Conference on Thermal Sensing and Imaging Diagnostic Applications
Douglas D. Burleigh; Jane W. Maclachlan Spicer, Editor(s)

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