Modern communication systems require extraordinarily stringent specifications on microwave and millimeter-wave components. In mobile and integrated communication systems, miniature, ultra-wideband and high performance filters and multiplexers are required for microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs). In satellite communications and wireless base stations, small volume, high quality, high power handling capability and low cost filters and multiplexers are required. In order to meet these requirements, three aspects are mainly pursued: design innovations, precise CAD procedures, and improved manufacturing technologies. This dissertation is, therefore, devoted to creating novel filter and multiplexer structures, developing full-wave modeling and design procedures of filters and multiplexers, and integrating waveguide structures for MICs and MMICs in Low Temperature Co-fired Ceramic (LTCC) technology.

In order to realize miniature and broadband filters, novel multiple-layer coupled stripline resonator structures are proposed for filter designs. The essential of the resonators is investigated, and the design procedure of the filters is demonstrated by examples. Rigorous full-wave mode matching program is developed to model the filters and optimize the performance. The filters are manufactured in LTCC technology to achieve high-integration. In order to obtain better quality than planar structures, new ridge waveguide coupled stripline resonator filters and multiplexers are introduced for LTCC applications. Planar and waveguide structures are combined in such filter and multiplexer designs to improve the loss performance. A rigorous CAD procedure using mode matching technique is developed for the modeling and design. To design wideband multiplexers for LTCC applications, ridge waveguide divider junctions are presented to achieve wideband matching performance. Such junctions and ridge waveguide evanescent-mode filters are cascaded together to realize the multiplexer designs. The design methodology, effects of spurious modes and LTCC manufacturing procedure are discussed.

Additional important issues of microwave filter and multiplexer designs addressed in this dissertation are: (1) Systematic approximation, synthesis and design procedures of multiple-band coupled resonator filters. Various filter topologies are created by analytical methods, and utilized in waveguide and dielectric resonator filter designs. (2) Dual-mode filter designs in circular and rectangular waveguides. (3) Systematic tuning procedure of quasi-elliptic filters. (4) Improvement of filter spurious performance by stepped impedance resonators (SIRs). (5) Multipaction effects in waveguide structures for space applications.