Research On The Field And Circuit Characteristics Of Non-uniform Transmission Line

Transmission lines are important components in the modern communication system and microwave high-speed circuit.The non-uniform structures of the transmission line can cause reflection,radiation,and coupling to the surrounding circuit,especially in the high-frequency band.These effects can even affect the normal operating of the whole circuit.Therefore,it is very important to study the circuit and field properties of the non-uniform transmission lines and to optimize their structures.In this dissertation,the extraction method,characteristics,and applicability of the distributed circuit parameters of the non-uniform microstrip line are studied by using the field-circuit combined method.Meanwhile the radiation mechanism of the asymmetric CPW is studied.The velocity compensated methods and the corresponding realistic compensation structures which can improve the transmitting performance of the asymmetric CPW efficiently are proposed.The main work and innovation points in this dissertation are as follows:1.The methods for extracting the distributed circuit parameters of the non-uniform microstrip lines with right-angle bend,chamfered bend and step are studied,and the relationships of the extracted circuit parameters with structural parameters, dielectric coefficients,and operating frequencies are analyzed.The different requirements on terminal load when employing the conventional and generalized transmission line equations respectively to extract the circuit parameters are discussed,and the results calculated by these two methods are compared.2.The influence of voltage calculation path on the extracted circuit parameters is studied,and the reason that causes this influence is analyzed.The optimal voltage calculation path on the bend microstrip line is given.3.The effectiveness and applicability of the extracted circuit parameters are studied for the first time.Through analyzing the transmitting performance of the equivalent circuits constructed by the extracted circuit parameters,the frequency application scope of the extracted circuit parameters are obtained by comparing the results of the equivalent circuit with those calculated by the full wave methods.The effect of the dynamic parameter parts involved in the extracted circuit parameters is further analyzed.4.The micro-resonant phenomenon at discontinuity of the bent microstrip line is found and studied.Through analyzing the variation of the micro-resonant phenomenon with structural and source parameters of the microstrip line,the reason that causes the micro-resonant phenomenon is found.Thc influence of the bent microstrip line with or without chamfering on the micro-resonant magnitude is studied.5.The odd-mode radiation mechanism of the asymmetric CPW is studied.The velocity compensated methods,which can suppress the odd-mode radiation and improve the transmitting performance of the asymmetric CPW,are proposed.Three kinds of the velocity compensation structures are also proposed,and the formulas for calculating the structural parameters of these three kinds of structures arc given when they are used to compensate the asymmetric CPW.6.The methods for solving the ratio of the propagation constant on the compensation structure to that on the conventional structure arc given.An approximate method for calculating the ratio of the propagation constant on the hole array structure to that on the conventional structure by using duty ratio are proposed.The propagation constant ratios on the typical velocity compensation structures are given,and their compensation effects are discussed.7.Three kinds of the velocity compensated CPW bends are designed and their compensation effects are analyzed,and the transmitting performances of these structures are also compared with that of the air-bridged structure.The velocity compensated CPW bends with corrugation and hole array are fabricated and measured.The theoretical results agree well with the measured results.