Development Of Complex Permittivity Measurement System Over Variable Temperature Ranges By Dielectric Resonator Method

High quality dielectric resonator is one of the key components of the microwavecircuits and systems. With the rapid development of microwave circuits and systems,most dielectric resonators will directly become an integral part of the microwaveintegrated circuit. However, it is still very important to develop new materials,especially materials with higher dielectric constant and low loss. Moreover, theoperating environment and temperature of microwave device could not be always thesame, so, to design microwave devices that meet well with the system indicators in anybad environment, we need know that how the complex dielectric constant and frequencytemperature coefficient of microwave dielectric materials vary with temperature.Therefore, it is essential to accurately measure the relative permittivity, loss tangent andfrequency temperature coefficient of dielectric resonator in variable temperatureenvironment for the research and application of dielectric resonator and material.According to the requirement of some institutes, the variable temperature test system forcomplex permittivity with dielectric resonator is developed.First of all, the paper has a further study of the complex permittivity test techniqueswith dielectric resonator at home and abroad. According to the requirements of thesystem indicators, and the advantages and drawbacks of different methods, we finallychoose the parallel plate resonator method. Meanwhile, we do more study about thetheory of parallel plate resonator method.Secondly, a theoretical analysis of the parallel plate resonator is made.Respectively, the eigen equations of the dielectric resonator is solved with the method ofexponential curve fitting and polynomial fitting, and the results derived from the twomethods are compared. Then the approximate resonant frequency of TE_0np high-ordermode is solved and the discrimination method of TE_0np mode is introduced. Fourmethods to solve the surface resistance are introduced. After a comparative analysis ofthe four methods, we chose one of them.Furthermore, the development process of test fixture is introduced，and someimportant consideration is pointed out. In order to meet with the test system’s requirements of variable temperature （temperature range-60℃¹60℃）, this paper alsodescribes the design of heating device, cooling device and temperature auto controldevice.Finally, the dielectric resonator test system is built up by integration of everymodule, which can measure the complex permittivity of dielectric materials atfrequency from1GHz to18GHz and at the temperature ranges from-60℃to160℃. Inconvenient to test for non-professionals, we also build an auto-test software. Somedielectric resonators are tested using the system, and the results are analyzed. Then thesource of the errors is analyzed and the error formula is derived.