Modified transmission-reflection method for measuring constitutive parameters of thin flexible high-loss materials |
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Authors: | Williams T.C. Stuchly M.A. Saville P. |
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Affiliation: | Dept. of Electr. & Comput. Eng., Univ. of Victoria, BC, Canada; |
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Abstract: | The transmission-reflection method is modified for measuring constitutive parameters of thin high-loss materials used as radar absorbers. The method uses a two-layer structure, consisting of a layer of thin flexible unknown material supported by a thicker rigid known material. The analysis and measurements focus on nonmagnetic samples of a high dielectric constant and loss factor and on the waveguide configuration in the X-band. A nonlinear least-squares optimization is used to obtain the complex permittivity from the measured scattering parameters. The uncertainty analysis presented facilitates selection of the support layer thickness. Simulations with the finite-difference time-domain method explore the effects of sample imperfections. Accuracy of a few percent can be achieved for a sample thickness of a fraction of a millimeter, provided that the thickness of the support dielectric is close to optimum and sample has only small surface imperfections. |
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