In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a bi-layer dielectric material using a Ku-band rectangular waveguide WR62. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a bi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the transmission lines theory, the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated the Sij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from bi-layer measurements and mono-layer measurements is presented.
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