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A Thickness-Unknown Method for the Low-Loss Dielectric Characterization from Free-Space Scattering Measurements



Sung Kim, David R. Novotny, Joshua A. Gordon, Jeffrey R. Guerrieri


A free-space measurement method is presented for the characterization of low-loss dielectric materials at millimeter-wave (MMW) frequencies that does not require any assumption of a priori knowledge of the sample thickness. The present method first employs only maximal and minimal envelopes of measured transmission scattering parameters to determine the real part \epsilon_r' of the permittivity of test materials. Subsequently, the thickness of the sample is estimated from epsilon_r' and frequencies for maximal and minimal peaks of the transmission scattering parameter, and then calculation of the imaginary part epsilon_r" of the permittivity easily follows. Our method is examined by measuring two cross-linked polystyrene (XLPS) samples, one polytetrafluoroethylene (PTFE) sample, and one polymethylpentene (PMP) sample in the frequency range of 220-325 GHz at incident angles of 0, 10, 20, and 30 degrees. Moreover, an explicit uncertainty analysis for the permittivity is derived, and uncertainties of the extracted complex permittivity are reported.
IEEE Transactions on Antennas and Propagation


Bistatic scattering, dielectric permittivity, free-space measurement method, fringing spectra, low loss materials, millimeter-wave (MMW) measurements, scattering parameter envelopes.


Kim, S. , Novotny, D. , Gordon, J. and Guerrieri, J. (2016), A Thickness-Unknown Method for the Low-Loss Dielectric Characterization from Free-Space Scattering Measurements, IEEE Transactions on Antennas and Propagation, [online], (Accessed April 16, 2024)
Created September 1, 2016, Updated March 22, 2019