Portable Ring-Resonator Permittivity Measurement System: Design & Operation

Report No. ARL-TR-5993
Authors: Gregory Mazzaro, Kelly Sherbondy, Gregory Smith, Marc Ressler, and Russell Harris
Date/Pages: April 2012; 54 pages
Abstract: A method for measuring complex permittivity using ring resonators is presented. The measurement is suitable for ultra-wideband ground-penetrating radar frequencies. The ring-resonator technique is portable, wideband, and can be performed in-situ, without disturbing the dielectric sample. Design equations and physical dimensions are presented for fabricating traditional rings at frequencies between 600 MHz and 2 GHz. The meander-line ring-resonator concept extends the effective measurement frequency range below 600 MHz. The measurement procedure is explained, step-by-step. Only a handheld vector network analyzer, coaxial cabling, and the ring resonators are necessary for the measurement. A Matlab script, which references lookup curves generated in FEKO, calculates the complex permittivity. Values for the real and imaginary parts of the permittivity can be generated as each sample is measured, or they can be generated after all of the samples have been measured. Data is presented for samples of soils and homemade explosive simulants.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2012