Research On Composite Planar Multilayered And Substrate Integrated Waveguide Structures And Component Design

With the rapid development of modern communication technology,higher requirements for component design in communication systems are put forward.Miniaturization,low-cost,easy-integration,and high performance have become fundamental design considerations for filters as frequency-selective components.In this work,equivalent magnetic walls are realized in composite planar multilayered and substrate integrated waveguide structures.A cavity with all its four sides composed of such virtual magnetic walls,referred to as an equivalent magnetic side wall cavity(MSWC),has lower resonance mode frequencies,so that the size of the designed cavity can be reduced.Based on such a cavity or its deformation or its multi-cavity stacking,various miniaturized band-pass filters and diplexer are designed.A metal via array is used to adjust the resonant frequencies or their spacing of the first two modes in an equivalent MSWC to form a single pass band.The cross-coupling and mode cancellation mechanisms in the structure produce three transmission zeroes in the higher outer band,allowing very high out-of-band rejection over a wide frequency range.In addition to the above narrow-band filter,this work also designs an ultra-wideband filter that maintains miniaturization while achieving a relative bandwidth of 75%.The originally degenerate modes TEMooi and TE100 of an equivalent MSWC are employed to design two different dual-band filters,in which metal posts and slots are introduced,respectively,in order to eliminate the mode degeneracy and achieve two passbands.To enhance the bandwidths in each case,two identical cavities are stacked and coupled by a common slot structure.The obtained passbands have a small center frequency ratio that can be adjusted by changing the parameters of the corresponding perturbation structure.The isolation between the passbands is improved by selecting the output port location to produce transmission zeroes.The structure of the presented diplexer is basically the same as that of the aforementioned dual-band filter adjusted by slots.On the other hand,the positions of the output ports are adequately chosen to separate the outputs of two mode signals.The cavity in the proposed triple-band filter is a deformed MSWC.In order to isolate its DC component,a metal via is inserted.This also generates the dominate MSWC mode that has a very low resonant frequency and does not exist in the MSWC without the via hole.Hence,a further filter size reduction can be achieved.The center frequencies of the designed triple-band filter are 2.27,5.99 and 9.50GHz,respectively.Its overall size is only 18.60×17.50×4.964 mm3 using substrates with relative dielectric constant of 3.66.