A method is proposed for measuring the dielectric constant E" and dielectric loss ~" of high-absorption dielectric materials by measuring the reflection of electromagnetic radiation with the aid of an adjustable quarter-wave matching plate of nonabsorbing material close to the dielectric surface.The dielectric properties of absorbing materials at microwave frequencies are frequently found by measuring the parameters of wave reflection from the investigated sample with an adjustable layer thickness [1][2][3]. While these methods are very suitable for measuring the dielectric properties of polar liquids, the necessity of adjusting the layer thickness make them useless for measurement of solid dielectrics.The method proposed here is intended for measurement of the dielectric properties of solid, high-absorption materials from their wave reflection characteristics. The dielectric layer thickness is made large enough for full suppression of the electromagnetic radiation penetrating into it, and wave reflection is varied by a quarter-wave plate of nonabsorbing material moving parallel to the ith surface of the investigated material.If material layer is thick enough to completely suppress the penetrating radiation, the modulus of the wave reflection factor p has the form Zin -Z 0 p=~,where Z o is the wave impedance of free space, Zin is the input impedance of the discussed system,Z and Zj are respectively the wave impedance of the coating and the plate, T~ = 2r~i/$., and $. are respectively the propagation constant and the wavelength in free space, and I is the distance between the matching plate of coating surface [1].To facilitate further discussion, let us consider the known expressions for the dielectric constant e" and dielectric loss 8" of the coating material, and for the dielectric constant e I of the matching plate:8,=n2(l_y2); eO=2n2y; 81=nl 'where n and n I are respectively the refractive index of the coating and the plate, and y is the dielectric loss factor of the coating material [4].
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