Design Of RF Filtering Devices Based On Multimode Resonator

The miniaturized and highly integrated RF front-end module is the core component of the wireless communication system,and it is the only way to connect the signal transceiver and the antenna.In the face of increasingly complex electromagnetic environments,devices with the frequency selectivity can make full use of spectrum resources,reduce link noise,and suppress adjacent channel crosstalk.In particular,miniaturized passive planar filters,duplexers and filtering power dividers are the core devices with frequency selectivity in high-density integrated front-end modules.This paper uses multi-mode technology to implement a variety of microstrip/IPD filters,SIW duplexers and SIW filtering power dividers.In addition,the isolation network embedded SIW is first applied to the design of duplexers and filtering power dividers,thereby further realizing the miniaturization of the device and reducing the insertion loss of the device.The main research contents and contributions of this paper are as follows:1.The miniaturized wideband bandstop filter based on multi-mode technology is proposed.In order to solve the problem of the large size of the ultra-wideband bandstop filter,this paper adopts a multi-mode technology based on a mixture of distributed parameters/lumped parameters,and uses the“C”section with capacitive loading to achieve fourth-order ultra-wideband bandstop response.In addition,different in-band rejections and bandstop bandwidths can be easily realized by adjusting impedances of the coupled line.In order to further realize the highly integrated and miniaturized ultra-wideband bandstop filter,this paper adopts the fully lumped multi-mode technology.Compared with the aforementioned ultra-wideband bandstop filter based on lumped/distributed elements,this lumped IPD ultra-wideband filter can achieve a smaller size and is more suitable for application in So C systems.2.The ultra-wide stopband and ultra-wideband IPD bandpass filters based on inductively loaded?-type units is proposed.Ultra-wideband bandpass filters are key components in broadband systems.However,there are many problems such as large size and poor out-of-band performance in plane strong coupling structure,stub-loaded technology and strong coupling between microstrip resonators and slot resonators.In order to solve the above problems,the?-type element with inductive loading is proposed for the first time,which has the characteristics of harmonic suppression and does not need coupling structure.Based on this decoupling unit,fifth-order ultra-wide stopband and ultra-wideband bandpass filters are implemented in IPD.3.Multimode HMSIW single-/double-band filters based on slot line loading is proposed.Compared with the lumped parameter elements and microstrip transmission,SIW is more suitable for high-frequency systems because of its high Q value.However,the size of single-band filter based on SIW is large and the out-of-band performance is poor.To solve the above problems,the HMSIW loaded with H-type slot and HMSIW loaded with double slot line can achieve the third-order filtering response.For the HMSIW with H-type slot,the wide stopband response can be achieved for different high-order modes of HMSIW and the H-type slot.For the HMSIW with double slots,by adjusting TE₂₀₁ mode to TE₁₀₁ mode for the slot,the wide stopband characteristics can be realized,and the size is further reduced.In addition,by using the first two modes of H-type slot and the first four modes of HMSIW,a third-order dual-band HMSIW filter is realized in a single cavity for the first time.Moreover,the operating frequency and bandwidth of the single-/dual-band HMSIW filters can be controlled independently,so that the flexibility of the design is realized.4.The compact filtering power divider/duplexer based on multi-mode technology and embedded isolation network is proposed.The filtering power divider with high isolation is widely used in the power amplifiers and feeding network of antennas.Especially,the filtering power dividers/duplexers based on SIW is suitable for high frequency system.However,all SIW filtering power dividers need additional isolation network to realize in-band isolation,which not only leads to the increase of the size,but also the insertion loss and amplitude/phase imbalance.In order to solve the above problems,the isolation network with embedded capacity is introduced in the cavity structure for the first time,and different isolation bandwidth can be sythesized.In addition,the slot loading technology and feeding technology can easily realize the wideband isolation characteristics.In addition,the embedded L-type isolation network is realized in SIW cavity for the first time.It can not only achieve high isolation of any two frequency bands,but also realize the miniaturization of the device easily.5.The UWB filtering power divider with equal ripple isolation by using a single resistor is sythesized.The isolation of ultra wideband filtering power divider is always difficult problem.In this paper,a novel filtering power divider based on single resistor and equiripple isolation is proposed for the first time.The bandwidth and out-of-band response can be sythesized.More importantly,only one resistor is needed to achieve the equiripple isolation in the band.Fortunately,the isolation in the band must be 6 d B lower than the return loss of the input port.The bandwidth,out-of-band suppression and in-band isolation of the proposed UWB filtering power divider can be accurately synthesized with only one resistor.