Techniques For Measuring The Electromagnetic Parameters Of Microwave Materials With High Permittivity In Broad Band

In recent years, microwave techniques are developed in a high speed. A great variety of antennas and microwave devices are of comprehensive use. The research and development of many high-performance microwave dielectric materials, toward the high permittivity and wide band direction, have attracted many scientists'attentions. Following this development, the research of the techniques for measuring the parameters of microwave dielectric materials in wide band becomes more and more urgent. This paper aims at methods and techniques for measuring the parameters of microwave dielectric materials with high permittivity, which has profound theoretical significance and practical value.At first, the normal methods for measuring the electromagnetic parameters of the microwave materials, network parameters method, are introduced, and the problems of these methods are discussed.Then, we prove theoretically that the higher-order modes, such as TE20 and TE01, with asymmetry electric fields do not exist in its mode-spectrogram, when the rectangle waveguide is symmetrically excited by the coaxial-line probe. By using the linear fraction transformation method, the compared measurements are made, which verify the validity of the theoretical results. For the Teflon samples, the precision for measuring their complex dielectric constant in the frequency band 7-16GHz is high. These measurement results also indicate that the operating frequency of the standard 3cm waveguide can reach 16GHz under some special conditions. If the aspect ratio of the rectangle waveguide r = 3, its operating frequency is able to achieve 19GHz. Our conclusion is of practical value for measuring the complex dielectric constant of microwave materials in broad band.At last, a double-short-circuit method for measuring the complex permittivity of the microwave material is proposed. The short circuit reflection coefficients of the material samples with two different thicknesses in the waveguide are measured, and a set of constraint equations is build, which is solved by using the Matlab software. The normalized characteristic impedance and propagation constant of the material are then determined uniquely. Three existing equations can be used to calculate the complex permittivity of the material. As a result, the multiple-solution problem existing in the scattering parameter method can be effectively overcome. Finally the compared...