| With the development of communication technology, the application of multi-bandsystem has been paid more and more attention. In order to cater to the requirements ofmodern communication systems, study on multi-band bandpass filter is becomingincreasingly important. Coupling theory as a filter design methods is gradually concerned byresearcher. The multi-coupled filter synthesis theory is currently also the focus of the study.On the basis of generalized Chebyshev filter, from proceed with characteristic polynomial, thecoupling matrix theory of multi-band bandpass microwave filters (dual-band filter andtriple-band filter) were studied using numerical analysis methods in this dissertation. Thefollowing works are completed.First, A basic theory of coupled filter and traditional single-band filter coupling matrixmethod is introduced, and to lay the theoretical foundation for the research content.Second, a coupling matrix synthesise method of dual-band filter is presented. Thismethod is based on single-band filter coupling matrix method. By properly combing twosingle-band filtering functions to achieve dual-band filter frequency response. The method isapplicable to a symmetric filter, also applicable to asymmetric filter, and simultaneouslysuitable to the even-order and odd-order dual-band filter.Third, a coupling matrix synthesise method of multi-band bandpass filter is presented.Combination of dual-band filter characteristic polynomial synthesized method, using aniterative technique to optimize unequal-ripple reflection zeroes and eventually getting aninitial theory coupling matrix to meet the design requirements of multi-band bandpass filter.Based on the proposed coupling matrix synthesis theory, several examples of numericalsynthesis of filter and design simulation examples of practical microwave filter are alsopresented in this dissertation. These examples have validated the synthesis theory and provedthat the theory is applicable for the design of microwave filters. |
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