Research On Filters And Multiplexers Based On SIW Multimode Cavities

Recently,the rapid development of modern wireless communication technology sets higher demands on microwave and millimeter-wave communication systems,within which high-performance,high-integration,low-cost,and low-loss components are badly required to realize more advanced communication systems.Multiband and wide-stopband bandpass filters(BPFs)and multiplexers based on substrate integrated waveguide(SIW)technique show the merits of compact size and low loss,attracting widespread attention and becoming a signficant research topic in modern communication systems owing to their applications to multichannel and low-interference field.In this dissertation,after investigating the resonant characteristics of SIW multimode cavity,multiple modes can be exploited to design SIW multiband BPFs and multiplexers based on proposed multimode cavities and multimode frequency and coupling controlling techniques,and multiple modes can be suppressed to design SIW wide-stopband BPFs and multiplexers based on various modes suppression techniques.The main contents are as follows:(1)SIW triple-band BPFs and triplexers based on SIW triple-mode cavities: SIW triple-mode cavity and the corresponding triple-mode frequency and coupling controlling techniques are proposed,with which the triple-mode frequencies and couplings can be flexibly controlled.The realizable triple-mode frequency ratios and coupling ratios in the SIW triple-mode cavity is obtained,and the design procedures of SIW triple-band BPFs and triplexers are systematacially summarized.By using different coupling topologies,two SIW triple-band BPFs and an SIW triplexer with flexibly controlled frequencies and bandwidths are synthesized and designed based on triple-mode frequency and coupling controlling techniques.(2)Wide-stopband SIW dual-and triple-band BPFs and triplexers based on multiharmonic staggered technique: For two conditions of sufficient or lacking design degrees of freedom in SIW cavities which are employed to realize stopband performance,different harmonic suppression solutions are proposed using multiharmonic staggered technique.A wide-stopband SIW dual-band BPF with closely spaced passbands,a wide-stopband SIW triple-band BPF,and a wide-stopband SIW triplexer are synthesized and designed for the first time based on triple-mode frequency and coupling controlling techniques,simultaneously realizing dual-or triple-band and wide-stopband performances.(3)Wide-stopband SIW single-and dual-band BPFs and diplexers based on multi-spurious modes suppression technique: A multi-spurious modes suppression technique is proposed for the first time by modifying the conventional intrinsic suppression technique,simultaneously realizing the suppression of multiple spurious modes.For different resonant frequency distributions,different multi-spurious modes suppression strategies are applied.The theoretical realizable stopband bandwidth is derived and the design procedures of wide-stopband using multi-spurious modes suppression technique are summarized in condition of single passband or dual passbands.Two wide-stopband SIW single-band BPFs,a wide-stopband SIW dual-band BPF,and two wide-stopband SIW diplexers are synthesized and designed with further extended stopband bandwidths.(4)Wide-stopband SIW dual-band BPFs and diplexers based on half-mode SIW rectangular cavity: Widely separated passbands and wide-stopband are simultaneously realized for the first time by using half-mode SIW rectangular cavity and intrinsic suppression technique for spurious modes.The realizable dual-mode frequency ratio and stopband bandwidth are derived and the constraint relationship between them is discussed,then the design procedures of wide-stopband SIW dual-band BPFs and diplexers with widely separated passbands are summarized.A wide-stopband SIW dual-band BPF and two wide-stopband SIW diplexers are synthesized and designed,further extending the resonant frequency ratio and stopband bandwidth of SIW dual-band BPF and diplexers.