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Abstract
Electromagnetic material characterization measurements are an important aspect of modern design. Rectangular waveguides are often used in the material characterization process to facilitate measurement since they are readily available and because rectangular samples can be easily machined and placed in the cross-sectional plane of the waveguide for reflection and transmission testing and subsequently analyzed using a simple theory [1, 2]. However, this technique can produce unacceptably large errors for high loss or highly reflecting samples due to a poor signal-to-noise ratio (SNR) for the transmission measurement.In this paper, a partially-filled waveguide method is presented that enhances transmission quality and accuracy in electromagnetic material characterization measurements. The partially-filled waveguide geometry improves transmission but leads to the excitation of higher-order modes. A mode-matching technique is developed here to accommodate the resulting waveguide discontinuity and a Newton root search method is utilized to subsequently extract the electromagnetic properties of the test sample. Experimental measurements for several materials will be presented at X-band frequencies (8–12 GHz) to verify the theoretical analysis.
