The Study Of Complex Permittivity Of Microwave Substrate Based On Microstrip Ring Resonator

Nowadays, microwave substrate materials have been widely used in microwavecommunication, remote sensing and other electronic and communication systems.Acquiring the exact complex permittivity of microwave substrates has become microwavesubstrate material producers’ and microwave circuit designer s’common concern. However,the microwave substrate materials from different manufacturers or different batches couldhave different complex permittivity. It has a significant influence on setting designparameters, production control and acceptance of purchased equipment. Therefore, it isimportant to detect the consistency of the complex permittivity of microwave substratesrapidly and conveniently. Research on the consistency measurement of the complexpermittivity of microwave substrates is based on this background.First，a microstrip ring resonator working at2.4GHz is designed and fabricated basedon the working principle of microstrip ring resonator. To miniature the microstrip ringresonator working at lower frequency, this paper innovatively utilizes the horizontalinterdigital structure to miniature the microstrip ring resonator which works at1575MHz.And it effectively reduces the size of microstrip ring resonator up to64%. Following, thispaper focuses on extracting the mathematical expressions of the complex permittivitybased on microstrip ring resonator method. With the method of combining simulation andactual measurement, the mathematical formula of complex permittivity based onmicrostrip ring resonator is finally extracted. After all the work, automated test software isdesigned. With this software, different batches microwave substrates are tested. The testingresults show that the automatic test system can effectively used in the complex permittivityof microwave substrate consistency measurement. At last, this thesis discusses therelationship of characteristic phase and complex permittivity of microwave substrate.The paper is divided into six chapters. Chapter1introduces different complexpermittivity measurement methods. All these methods can sum up to resonant method andnon-resonant method, and the advantages and disadvantages of each method are discussed.In Chapter2, an introduction to the working principle of microstrip ring resonator is firstgiven. On this basis, a microstrip ring resonator which works at2.45GHz is designed and fabricated. Then, after introducing the concept of horizontal interdigital structure, thestructure is innovatively utilized to miniature the microstrip ring resonator which works on1575MHz. Chapter3mainly introduces the derivation of the complex permittivity ofmicrowave substrate. Firstly, the relationship between the dielectric constant and frequencyoffset is discussed. Secondly, the algorithm of the loss tangent and the Q factor hasresearched. The complex permittivity automatic test software is designed in Chapter4, andthe modules of the system are introduced in details. Then, FR4and F4B microwavesubstrates are tested by this system, and the test results are analyzed. The results show thatthe system is effective. In Chapter5, the characteristic phase inequality of S-Parameters forlossy network is introduced. Then a research on the relationship between characteristicphase and the complex permittivity of microwave substrate is carried on. With thecharacteristic phase test software, numeric and test results are analyzed. Finally, the entirework is summarized and the future prospect of the relevant research work is presented inChapter6.