Research On Microwave Multilayer Differential Filters With Hybrid Microstrip-Line And Slotline Structure

Following the high-integrated developing trend of modem microwave communication systems,on one hand,microwave planar passive components are going to be designed on multilayer with multiple kinds of transmission-lines,while vertical transitions are critical components;on the other hand,there will definitely be massive electromagnetic interference between close placed microwave components,so differential filters with the property of common-mode(CM)noise suppression are drawing increasing attentions.Under the above developing background of modem multilayer communication systems,deep research and design have been implemented on wideband vertical transitions and differential filters with intrinsic CM rejection in this dissertation.The main work can be summarized as follows:1.Multi-resonant modes in slotline resonator are properly excited and applied on design of wideband vertical transition between microstrip-lines on different signal layers;design principle of multimode wideband theory and design method of circuit model synthesis are ultilized to design these transitions.As examples,vertical transitions formed by one/two multimode slotline resonators are designed and fabricated.Their simulated and measured results prove that these vertical transitions have expected wide operating bands and good in-band flatness.The proposed design principle and design method are verified as well.2.Two differential wideband filters with intrinsic CM rejection are proposed,both of which are constructed with multimode slotline resonators fed by differential feeding schemes.They are expected to have intrinsic rejection in CM by virtue of the filed mismatch in their feeding schemes,whereas multi-resonant modes of slotline should be excited and used for wideband responses in DM.For verification,these two filters are designed and fabricated.Their simulated and measured results verify the design principle of multimode wideband theory and the design method of circuit model synthesis.The achievable DM fractional bandwidths of these filters are within the range of about 100%-140%.3.A novel kind of strip-loaded slotline resonators is proposed for design of differential wideband filters with intrinsic CM rejection.The proposed resonators are expected to have CM rejection themselves as inherent properties,so that their feeding schem are not restricted to differential feeding schemes.With general parallel coupling feeding shceme,the resonators are further expected to have mode distribution properties in DM which are extremely suitable for wideband applications.Based on theory above,two differential filters are designed and fabricated.Their simulated and measured results show that they possess many merits,such as wide bands,low insertion losses,good in-band flatness,simple design method and so on.The differential filters are applied for DM fractional bandwidth of about 67%-94%.4.In order to design a differential dual-mode dual-band filter with intrinsic CM rejection,a general and simple design method for hybrid multimode resonator is proposed.The hybrid multimode resonator which has the CM rejection as an inherent property is easily developed from its single-ended conterpart.Using this proposed design method,a hybrid resonator which can be used to design either a differential wideband filter or a differential dual-mode dual-band filter is completely designed.The validity of the relative design theory and design method is verified by the filters' simulated and measured results.5.Besides multimode resonators,coupled resonators are investigated to design differential filters with intrinsic CM rejection applied for DM fractional bandwidth<70%.Two differential filters are proposed:(1)with input/output microstrip-line feeders,three slotline resonators are inductively coupled through anti-parallel coupled slotlines to construct a differential filter.The filter is simulated and measured with low insertion-loss and harmonic suppressed property;(2)a dual-wideband differential filter is presented on strip-loaded slotline resonators and strip-loaded coupled slotlines with microstrip-line feeders.The simulated and measured results prove the feasibility of the wideband coupling scheme and the respective dual-wideband filter.