Research Of Substrate Integrated Hexagonal Cavity (SIHC) Filter With Multiple Transmission Zeros

Filter is one of the most widely used components in communication systems. Accordingly, to meet the development needs in high performance, low weight and high integration, researches should be done in exploiting filter with low loss, high selectivity and miniaturized size. Filters based on Substrate Integrated Waveguide (SIW) technology are not only superior for their high quality factor(Q) and lower loss as conventional waveguide, but also for their characteristics such as low profile, low weight, low cost high integration and easy to be fabricated. So it is extensively studied in high performance miniaturized filter design. The main purpose of the research in this paper is to exploit SIW filters with miniaturized size and multiple transmission zeros (Multiple-TZ) in virtue of hexagonal cavity. Cross coupling, mixed coupling and multi-mode technology are mainly implemented in this research.Firstly, some design basis of SIW filter is introduced in the paper. Coupling matrix theory is deducted to prepare for filter design. Characteristics of hexagonal cavity are analyzed after comparing with circular and rectangle ones. Coupling structures between coplanar and different surface of hexagonal cavities are explored as well.Secondly, cross coupling technology is introduced into the design of muti-layer substrate integrated hexagonal cavity (SIHC) filter afterwards. N-2zeros are obtained by using this technology while designing N-order SIHC filters. The measurement results of the filters fabricated by LTCC technology agree well with EM full wave simulation while their configurations are reduced than conventional planar filters.Mixed coupling (MC) is implemented to design muti-layer SIHC filter for the sake of obtaining more zeros. By employing MC structure in direct coupling path and cross coupling path,N-order SIHC filers generate N-1zeros and selectivity of SIHC filters is improved as a result.Muti-mode technology is introduced into the design of SIHC filters finally. The proposed N-order dual-mode filters realize N and N+1zeros. By utilizing input/output structure of different angles, the single cavity SIHC filter obtains3zeros at a maximum. In addition, MC is employed into source/load coupling path to generate additional zero. In the end of this paper, dual-mode hexagonal cavities are implemented into design of multi-layer SIHC filter which constructed by using PCB process and the high performance miniaturized SIHC filter is suitable for MMW communication applications.