Resonant properties of a multilayer strip-slot transition and its application for microwave measurements of dielectric properties of materials
Authors: Fomin D.G. , Dudarev N.V. , Darovskikh S.N. , Klygach D.S. , Vakhitov M.G. 
Published: November 2021

Statement of the problem: One of the actual problems of applying radio materials at high and ultrahigh frequency ranges is the problem of increased requirements for the accuracy of assessing their dielectric properties. Currently, non-resonant and resonant methods are applied to assess the dielectric properties of radio materials at the frequency ranges indicated above. Non-resonant methods are expedient for application in non-destructive testing of large-area sheet materials. Their implementation requires the application of an expensive vector network analyzer. Resonant methods are applied with a limited amount of the test material or in its powder state. In the implementation of resonant methods the main investigated parameter is the displacement of the frequency of the electrical resonance. As a consequence, only the amplitude values of the transmission and reflection coefficients need to be known. This feature makes it possible to carry out microwave measurements for the resonant method applying a scalar network analyzer which has a lower cost compared to a vector network analyzer. That feature is an advantage in some cases. One of the promising directions in the development of the resonant measurement method is its implementation based on applying of a volumetric-modular technology. In particular its implementation that based on application of a multilayer strip-slot transition. The problem with this approach is the lack of researches in terms of the effectiveness of the application of the multilayer strip-slot transition as a device with a tunable frequency of electrical resonance. Aim: The aim of this article is to present a resonant method based on the application of the multilayer strip-slot transition as a basic measuring device. Such a design solution for the implementation of resonant microwave measurements has no analogues. This determined the conduction of current research. The task of which is to theoretically and experimentally substantiate the effectiveness of applying a multilayer strip-slot transition to implement the resonant method for measuring the dielectric properties of materials. Results: The results of theoretical and experimental studies of the resonance properties of the multilayer strip-slot transition are presented. Its application makes it possible to realize an original volume-modular device for the resonant method of measuring the dielectric parameters of materials in the microwave range of wavelengths. The theoretical research is based on the development of an equivalent circuit, which is presented in the form of a cascade connection of four-port networks. The results of mathematical simulation of the multilayer strip-slot transition prove the possibility of implementing on its basis the resonance method for measuring the dielectric parameters of materials in the microwave range of wavelengths. Experimental studies were carried out on a sample of a volume-modular device with the multilayer strip-slot transition. The test material was a powder representing barium hexaferrite BaFe10Ti2O19 partially substituted by titanium. The coincidence of the results of mathematical simulation and experimental studies of the frequency-selective properties of a multilayer strip-slot transition is more than 95%. The error in assessing the permittivity of the used powder material based on the results of theoretical and experimental studies does not exceed 4.5%. Practical significance: The results of the research showed the possibility of applying of the multilayer strip-slot transition as a basic element for the implementation of the resonance method for measuring the dielectric properties of materials. The advantages of the proposed design are compactness and the ability to measure the dielectric properties of powder materials using scalar network analyzers.