M.W. Hyde IV, M. Havrilla, and P. Crittenden (USA)
R-card, transmission, permittivity, resistivity, and material measurements Figure 1. 7 GHz, H-pol, theoretical and average measured monostatic RCS of an 892 Ω/sq (DC resistivity) R-card wrapped around a foam cylinder. Experiment has shown a ±0.5 dBsm uncertainty in compact range RCS values.
A free-space and waveguide technique for determining the relative permittivity and ultimately the resistivity of an R-card using the forward transmission coefficient is presented. The exact solutions for S21 are derived in sections II and III. Utilizing the Maclaurin series for sine and cosine, approximations of the exact solutions are made which are simpler to solve than the exact expressions. The accuracy of the approximations is directly related to the R-card’s thickness and wave number. Free-space (2 GHz – 18 GHz) and waveguide (8.2 GHz – 12.4 GHz) measurements were made of two R-cards of differing thicknesses and resistivities to demonstrate the method.
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