Research On High Accuracy Testing Technology For Dielectric Properties Of Quasi Optical Cavity Method

Microwave millimeter wave technology has been widely used in radar,communications,biomedical and other fields.In millimeter-wave components,the use of material properties can have a large impact on the system.Dielectric properties are important parameters that characterize material properties.Accurately obtaining the dielectric properties of millimeter-wave materials has important theoretical and engineering implications.At present,the material dielectric parameter measurement mainly develops to high precision,high frequency,wide frequency band,and automation.At the same time,material non-destructive testing is also a hot research direction.This article will study the high accuracy of materials testing.The quasi-optical resonator has the characteristics of convenient operation,simple mode,high quality factor,etc.So we use the quasi-optical cavity method for high-precision study of the complex permittivity test.First of all,this paper introduces the development of dielectric parameter testing technology at home and abroad.Then the Gaussian beam theory is used to align the optical cavity structure for field analysis.The simulation software is used to draw the energy and field distribution of the semi-symmetric quasi-optical cavity structure,and the optical cavity method material testing theory is introduced in detail.According to the index of the paper,the corresponding cavity structure size is determined,and the design of the quasi-optical cavity can work in both Ka and W bands at the same time.Secondly,we analyze the mismatch between Gaussian beam phase plane and spherical reflector and design a modified semi-symmetrical quasi-optical cavity system with exactly matching isophase surfaces.Using HFSS electromagnetic simulation software,two sets of quasi-optical cavity models were simulated and compared.For the analysis of phase mismatch between Gaussian beam and other surfaces on the surface of the sample material,the formula of the resonant frequency is corrected by using the perturbation theory.According to the thesis index,we design a coupling device that can be applied in Ka band and W band.Then we formulated relevant test specifications.The test system is perfected and the system structure is improved to eliminate high-order modes and improve the test accuracy.Finally,two sets of different concave mirror quasi-optical cavity test systems were constructed using a vector network analyzer.Write this test software by VC++.Test the standard sample materials,compare and analyze the test results of the two test systems,and analyze the errors caused by the parameters extraction and processing of the cavity in the test system.