Researches Of Microwave Filters Based On Substrate Integrated Waveguide

With rapid development of wireless communications and radar technology etc., microwave and millimeter-wave circuits and systems of high performance draw much attention. The circuits are undergoing the process of small size, light weight, low cost, and high reliability due to the commercial and military requirements. Microwave filter is one of the key components in microwave and millimeter-wave systems, whose low insertion loss, high selectivity, high performance could greatly improve the performance of the system.Substrate Integrated Waveguide (SIW) is a novel guided-wave structure, capable of the design of devices requiring low insertion loss (IL), low radiation loss and high Q. SIW and the conventional metal rectangular waveguide are of the similar propagation characteristics. However, Many processes including the standard PCB, LTCC and Thin-Film can be applied to the fabrication of SIW. Meanwhile, in order to reduce the size of SIW devices when designed to work in the lower microwave band, a novel technology named "half mode substrate integrated waveguide"(HMSIW) is just proposed by the State Key Lab. directed by Prof. W. Hong. The new structure could keep the original performance of SIW with nearly a half reduction in size.The main contents of this thesis are listed as follows:1,Basic characteristics of SIW and HMSIW are studied. Designs of SIW-Microstrip and HMSIW-Microstrip transitions are introduced.2,Traditional design methods of the filter are applied to SIW. For the structures of metallic posts and dielectric posts, corresponding FORTRAN programs based on dichotomy algorithm are designed for the synthesis of the dimensions of the two kinds filters. The agreements between simulated and measured results of the filters working in the K-band show the design methods are correct. Further more, an inductive windows SIW filter and an E-plane metallic-via SIW filter working in the Ka-band are also designed and simulated with HFSS.3,In order to reduce the size of SIW devices, we have tried to design an inductive posts HMSIW filter working in the X-band. With the microstrip taper embedded into HMSIW, a novel compact wideband band-pass filter based on the high-pass characteristic of HMSIW and the low-pass characteristic of a microstrip low-pass filter is simulated and measured, the results of which show that the design method is correct.