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Quantitative Images of Antenna Patterns Using Infrared Thermography and Microwave Holography

Published

Author(s)

J. D. Norgard, J. E. Will, Carl F. Stubenrauch

Abstract

This paper describes the application of microwave holography to infrared (IR) thermal images of electromagnetic (EM) fields for the purpose of measuring near-field radiation patterns of antennas. The phase of the field is retrieved from IR thermograms (magnitude-only thermal images of the field) measured in the near-field of the antenna using microwave holography. One method to extract the phase is to use an iterative Plane-to-Pland (PTP) two-dimensional (2D) holographic phase retrieval method. After the phase is recovered, the near-field thermographic/holographic data can be processed to determine the complex intensity (magnitude and phase) of the field at any distance in front of the antenna under test (AUT). Of particular interest is the far-field radiation pattern of the antenna or, especially for phased array antennas, the aperture source-plane distribution. Numerical simulations were performed to determine the feasibility, accuracy, and sensitivity of these IR thermographic/holographic phase-retrieval techniques. The advantages and disadvantages of the technique are also discussed. To demonstrate the feasibility of the technique, actual IR thermograms were measured at AFRL/RRS (Rome Reasearch Site) in Rome, NY for the PTP case. A simple planar 6x6 phased array patch antenna was tested. The phase retrieval results are presented and compared to the known results for this antenna, as measured on the near-field range at NIST/Boulder using standard hand-wired probes. The agreement between the results for this antenna is very good.
Citation
International Journal of Imaging Systems and Technology
Volume
11
Issue
4

Keywords

antenna measurements, far-field patterns, infrared measurements, microwave holography, phase retrieval

Citation

Norgard, J. , Will, J. and Stubenrauch, C. (2000), Quantitative Images of Antenna Patterns Using Infrared Thermography and Microwave Holography, International Journal of Imaging Systems and Technology (Accessed February 27, 2024)
Created October 31, 2000, Updated October 12, 2021