Research And Application Of Passive Circuits Based On Interdigital Coupled Structures

Microwave passive components including couplers and filters are important parts of microwavesystem. With the rapid development of communication technology, on the one hand, thecharacteristics such as bandwidth and loss of passive components are needed to meet severerrequirements. On the other hand, we hope the manufacturing of passive components are moreeconomical and simplified. Interdigital coupled structures have been widely used in passivecomponents to realize tight coupling and widthband.In the develop process of the microwave transmission line, microstrip and coplanar waveguideshave been widely used in sorts of microwave system due to their advantages including simplestructure, easy integration and low cost. By chosing the suitable transmission line according todifferent requirement, we can easily realise systemic construction and obtain the betterperformance.This thesis mainly contains three objects as below based on relevant research status and thefoundational theory,1. The synthesis of four-line interdigital structure and interdigital coupler with defected groundstructure is presented. Four-line interdigital structure has an accurate restriction on coupledline-width and gap-width, by adding defected ground structure in coupled line position, moresimplified manufacturing requirement and minor coupled intensity variation can be realized.2. The six-port network based on micorstrip feeding and CPW coupling is proposed. Thenetwork has one input port, one direct port, two coupled ports and two isolated ports. It can be usedas three-way power divider. In addition, its’ structure is simple and it is compatible with printedcircuit processing technology.3. The analysis of a multi-mode resonator coupled with two parallel lines and a four-lineinterdigital coupling suited resonator is presented. After that we describe a wideband filter based onthe interdigital coupling suited muti-mode resonator. By allocating the first three resonancefrequency in4.2GHz~8.2GHz, the filter realizes a wide passband. By offseting the fourth resonancefrequency with stub-loaded structures, the stop-band reaches to14GHz.