| This paper is based on the design of inline filters and multiplexers, and studied therelated filter structures and synthesis design methods.Firstly, frequency transformation, circuit model and delay calculation were givenas the basic theories. This paper introduced how to extract transversal coupling matrixand transform the initial matrix to arrowheaded matrix. Then it described how toachieve the topological structure of cascaded trisection and cascaded quartets.Secondly, star-junction structure of multiplexer was introduced, and the synthesismethod was summarized. Considering multiplexer with common cavity could only beused in the condition of narrow bandwidth, the synthesis of multiplexer withoutcommon cavity was presented. For conveniently verifying the correctness of the matrix,the method that the circuit model was automatically generated by compiled softwarescript was adopted. The synthesis results of the two types of multiplexer were verifiedby an integrated approach and automatically generated circuit model.Thirdly，a design example of triplexer was given in3.61GHz~4.39GHz. Thestructure of each channel used inline filter structure with orthogonal coaxial cavity. Thispaper analyzed the structure of novel inline filter and traditional inline filter. There weretwo methods to realize the design of traditional inline filter. Novel inline filter had thecharacteristics of more compact structure and better stability when compared withtraditional inline filter. The coupling matrix proposed synthesis approach was used todesign the public port and the multiplexer was overall optimized, which used coaxialcavity structure.Finally, the designed multiplexer was manufactured and tested. The result wassatisfactory and agreed with the simulation. It was also proved the proposed synthesismethod of multiplexer without common cavity and the program automatically creatingcircuit model were convenient and effective, which played a great role in directing theactual engineering design. |
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