Research Of Substrate Integrated Waveguide Filters Based On Low Temperature Co-fired Ceramic Technology

Substrate integrated waveguide (SIW) filters not only have high quality factor, lowinsertion loss and high power capability which are similar to the conventional metalwaveguide, but also have the characteristics of easy integration and fabrication.Particularly, the application of low-temperature co-fired ceramic (LTCC) technologymakes the realization of multilayered SIW filters with compact size, light weight andhigh performance possible, owing to its three dimensional integration characteristic,low-tolerance in manufacturing process, and low loss of high-frequency ceramicmaterials. Based on the basic theory of SIW technology and the LTCC3D structure, thisdissertation presents a series design of multilayer SIW filter with the features ofcompact size, high integration and high selectivity. It is summarized as follows:Firstly, the elementary principles of design and process on the LTCC multilayerSIW filters is systematically illustrated, which including resonator cavities, transitions,coupling manners of SIW, and features, materials and processes of LTCC. In addition,the analyses and optimizations of several key procedures during the manufacturingprocess are emphasized to lay the foundation for later design and fabrication ofmultilayer SIW filters.Secondly, several novel SIW filters with LTCC multilayer structures are proposedin this dissertation. Based on the canonical cross-coupled topology, multilayerrectangular SIW filters are designed and fabricated to verify the feasibility of multilayerSIW filters in LTCC structure. Subsequently, the hexagonal SIW resonators which cancombine flexibility of rectangular cavities and performance of circular cavities, arepresented for the first time. Then the practicability of the proposed hexagonal SIWresonators is proved by constructing planar and multilayer hexagonal SIW filters.Whereafter, to reduce the sizes of the SIW filters and improve their selectivities, thecoupling topologies of multi-transmission channels are investigated in this dissertation.Then three types of SIW filters with these topologies are proposed as follows. A SIWfilter with multilayer modified doublet (MMD) is proposed. The MMD comprises two resonators that are not coupled to each other, whereas the two resonators are placedbelow and above the I/O SIW, respectively. The proposed filter has two transmissionzeros which can be controlled flexibly by adjusting the coupling strength and modifyingcoupling manner. Besides, a compact SIW symmetric filter with source-load coupling ispresented. The number of its transmission zeros is same with the order of the filter.Moreover, multilayer modified trisection (MMT) and its applications to SIW filters arepresented. In virtue of flexible coupling manner of multilayer structure, the proposedfilters exhibit the merits of both miniature size and high selectivity.Thirdly, to obtain more signal transmission paths and zeros for improving stopbandcharacteristics without increasing the sizes of SIW filters, several novel SIW filters withan interdigital slot-line (ISL) to introduce mixed coupling into two cavities are proposed.Those filters with mixed coupling structures, including the SIW filter with MMD, thesymmetric SIW filter, and the SIW filter with MMT, are studied and discussed,respectively. An additional signal path can be achieved by introducing mixed couplinginto SIW filters, which can add a transmission zero in the passpand without increasingthe sizes of the filters.Finally, the SIW dual-mode filters with simple structure and high performance areproposed. The characteristics, resonator modes, feeding structures, and the synthesismethods of the SIW dual-mode filters are analyzed and discussed. A novel dual-modeSIW filter with mixed source-load coupling is presented. The proposed filter with singlecavity could have three transmission zeros to obtain low insertion loss and highselectivity. Furthermore, a LTCC multilayer SIW dual-mode filter is designed andfabricated. The measured results show good agreement with the simulated ones andvalidate the structure of the proposed filter. Compared with the conventional planar andsingle-layer structure, the multilayer dual-mode SIW filter exhibits the features withbetter selectivity, smaller size, and higher integration.