Abstract-This paper presents an improved method for microwave nondestructive dielectric measurement of layered media using a parallel-plate waveguide probe. The method bases on measuring the S parameter S 11 or reflection coefficient from the N -layer media over the range of 1 to 10 GHz. Formulation for the aperture admittance is presented which allows the solving of the inverse problem of extracting the complex permittivity for two cases of the media, (1) one that terminates into an infinite half-space, (2) one that terminates into a sheet conductor. Our theoretical analysis allows the study of the effects of air gaps and slab thickness on the probe measurements. Through numerical simulations, the ability to use the proposed method for dielectric spectroscopy and thickness evaluation of layered media is demonstrated.

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