Research And Design Of Miniaturized Multi-passband Filter Based On LTCC

The diversification of communication technologies puts forward higher requirements for the ability of communication terminals to simultaneously handle different services.Multi-band systems will become one of the development trends of communication technologies in the future.Multi-band filter is one of the most important passive device in the future multi-band systems.Multi-band filter as an important passive devices future multi-frequency system,its size has an important influence on the volume of multi-frequency systems,and the miniaturization of multi-band filters is one of the problems to be solved in the field of industrial design.Low temperature co-fired ceramic(LTCC)technology uses three-dimensional integration of low-loss materials.Microwave devices designed with LTCC technology are characterized by small size,low cost,and good performance.In this thesis,miniaturized multi-band filters are researched and designed based on LTCC technology.The following research results were obtained:(1)A stub-loaded multi-mode resonant structure is analyzed,and an equivalent capacitance technique is employed to miniaturize the multi-mode resonant structure.A quadruple-mode resonant structure and a sextuple-mode resonant structure are proposed.The quadruple-mode resonant structure is analyzed in detail by the odd-even mode analysis method.A dual-band filter and a triple-band filter are designed based on the two resonant structures.The performance of the two filters is exceptional.The sizes are both 4.8mm×4.2mm×1.5mm.(2)The step impedance resonance(SIR)structure is analyzed,and a dual-band filter is designed by SIR using its harmonic adjustable characteristics.The multi-layer structure is adopted for miniaturization design,and an unequal shielding layer is added between the high and low impedance stripline layers to reduce the line width difference between the high and low impedance striplines,and to suppress the coupling between the high and low impedance striplines.A defected ground structure is added to optimize the stop band rejection performance of the filter.The filter performance good and the size is 4.5mm×3.2mm×1.5mm.(3)Three multi-band filters are designed by combining miniaturized filters.The port impedance variation of the filter before and after the combination is analyzed.Three multi-passband filters have been designed,including: A dual-band filter is designed by cascading a miniaturized ultra-wideband filter and a lumped band-stop filter;another dual-band filter is designed by paralleling two miniaturized parallel coupled band pass filters,matched by adjusting the taps;a quadruple-band filter is designed by paralleling a miniaturized band pass filter and a miniaturized triple-band filter.The three filters performance good.The size of the cascaded dual-band filter is only 8.8mm×3.2mm×1.5mm.The size of two parallel multi-band filters are both less than 6.2mm×4.2mm×2.8mm.