Design of Microwave Cavity Filters
The Microwave Filter Design Book [1 ] provides established design equations for the design of Tchebyscheff combline and iris-coupled band pass cavity filters. The design equations are organised in the form of tutorials and illustrated with examples. The s
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Design of Microwave Cavity Filters
Abstract The Microwave Filter Design Book [1] provides established design equations for the design of Tchebyscheff combline and iris-coupled band pass cavity filters. The design equations are organised in the form of tutorials and illustrated with examples. The successful industrial experience in complying with customer requirements in the frequency band, (1.0–4.5) GHz for cavity filters are blended with the illustrations. Polynomials are fitted to the relevant design graphs using Lagrange interpolation technique to eliminate the need to refer the graphs Software could be developed for the tutorials including the polynomials. Guidance for the selection offilter parts, methods of end coupling and tuning of filters in frequency and time domain are provided.
7.1 Introduction Design of cavity filters is the process of converting the electrical specifications of the filters into the mechanical dimensions of cavity block, resonators and other parts using design equations. The Microwave Filter Design Book [1] provides established design equations and graphs for computing the mechanical dimensions both for maximally flat and Tchebyscheff types of filters. The application of the design equations is successful in complying with customer requirements in the frequency band, (1.0–4.5) GHz for the cavity filters. The extension of the frequency bands is also feasible using the design equations of the Microwave Filter Design Book. The design equations and graphs available in the various chapters of the Design Book are organised in the form of tutorials and the design of Tchebyscheff combline and iris-coupled band pass filters are illustrated with examples. Polynomials are fitted to the relevant design graphs using Lagrange interpolation technique to eliminate the need to refer the graphs. Software or Excel tool could be developed for the tutorials for repetitive designs. Practical information for the design of parts of the cavity filters, types of end coupling and tuning of filters are presented in detail. D. Natarajan, A Practical Design of Lumped, Semi-Lumped and Microwave Cavity Filters, Lecture Notes in Electrical Engineering, DOI: 10.1007/978-3-642-32861-9_7, Springer-Verlag Berlin Heidelberg 2013
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7 Design of Microwave Cavity Filters
Fig. 7.1 Design dimensions of combline band pass filter
7.2 Combline Band Pass Filter The general structure of combline band pass filter without side cover plate is shown in Fig. 7.1 indicating the mechanical dimensions that need to be computed for the piece parts of the filter. The number of filter sections (resonators) is limited to three in Fig. 7.1 for simplicity. Technical information for the design of the piece parts of combline filter is presented before computing the design parameters of filters.
7.2.1 Cavity Block Cavity block is milled from a solid aluminium block with one side open. The inside corners of cavity block are finished with radius. Symbols, l, h and b designate the internal length, height and width of cavity. The wall thick
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