Research On Low Loss Miniaturized Circuit Based On Substrate Integrated Waveguide

With the rapid development of modern microwave and millimeter wave circuit system,its function is more and more complex,the requirements for its electrical performance specifications is higher and higher,the volume of circuit is smaller and smaller.In general,the whole system is developing rapidly to the direction of high integration,miniaturization,multiband,multimode,multifunction and low cost.Therefore,low loss and miniaturized microwave/millimeter wave technology is very important for the development of high-performance wireless communication system.Substrate integrated waveguide(SIW)is a new type of planar guided wave structure.The appearance of SIW conforms to the development trend of high density and miniaturization of microwave and millimeter wave circuits.This kind of integrated waveguide not only keeps the advantages of traditional waveguide,such as low loss,high Q factor,high power capacity,self-consistent electromagnetic shielding structure,but also has the advantages of low cost,high integration and easy fabrication.The emerging substrate integrated waveguide technology has become an important choice for microwave and millimeter wave circuits.However,due to the cut-off frequency of SIW,which is related to its width,the application of SIW is faced with the problem of large size,which restricts its further application in the microwave frequency band.In this paper,the low loss and miniaturization of SIW circuit are realized based on multimode technology and multifunction technology.The way of combining multilayer technology,dual-mode technology,multiband technology and multifunction technology is deeply studied to better realize low loss and miniaturization SIW circuit.A series of low loss and miniaturization dual-mode filters and filtering couplers are designed and fabricated.The main works and innovations of this dissertation are listed as follows:1.In order to solve the problem that single-mode SIW cavity and cavity filter are too large and inconvenient to be applied,and many cavities need to be cascaded to achieve high selectivity,which leads to the increase of loss,a multilayer dual-mode filter based on the substrate integrated circular cavity(SICC)is proposed in this paper.For the first time,a multilayer dual-mode circular cavity filter with high stopband rejection,low loss,miniaturization and high selectivity is realized in the multilayer SIW circuit by adjusting the positional relationship between the coupling slot and the input /output port.By adjusting the geometric parameters of coupling slot and SIW cavity,the bandwidth,out of band rejection and return loss of the filter can be controlled.The proposed dual-mode filter combines multilayer technology and dual-mode technology,which are successfully applied to the design of SICC filter.To solve the problem that a single type of dual-mode SICC can only form a transmission zero in the upper side band,while the lower side band has a limited level of rejection,different shapes of dual-mode SICC and substrate integrated elliptical cavity(SIEC)are combined together to realize multiple transmission zeros in this paper.The proposed dual-mode complementary filter has better filtering response and effectively combines with multilayer technology to realize the low loss and miniaturization design of SIW circuit.For the first time,complementary dual-mode circular cavity and elliptical cavity resonators are introduced into the multilayer SIW circuit.A multilayer dual-mode filter with low loss,elliptical response,compact structure and good performance is obtained by using the different transmission zero positions of the dual-mode SICC and SIEC.2.In view of the limited topology of existing couplers and the difficulty of matching with the required signal transmission direction in practical application,this paper proposes several new filtering couplers based on mixed shape SIW cavity(MSSIW)for the first time,which are featured with miniaturized structure and arbitrary port direction.Then,the equivalent circuit principle and coupling matrix method are used to analyze the topological structure of the coupler,and the initial value of design parameters is calculated accurately.These new type couplers are easy to match the desired transmission direction,without introducing additional bending transition,thus reducing the overall size of the circuit to a certain extent.The MSSIW resonator filtering couplers proposed in this paper are more suitable for the development of high-density and miniaturized microwave/millimeter wave systems,and have important scientific significance and broad application prospects.3.To solve the problem that filtering couplers based on coupling resonators suffer from limited bandwidth,low level of out band suppression,and not suitable for wideband applications,a new type of wideband filtering coupler with high selectivity based on half mode integrated waveguides(HMSIW)is proposed in this paper.Normally,in order to improve the out of band rejection characteristics,it is necessary to load multiple resonators on each port of couplers,which will also lead to many problems,such as the increase of loss and circuit size.This paper proposes a new solution to avoid the above problems.This improved method can combine multilayer technology and HMSIW structure at the same time,and the size of coupler is significantly reduced.A novel ginkgo leaf slots(GLS)unit is etched on the top layer of HMSIW to realize the filtering coupler with this multifunctional structure.Because the structure integrates two functions of bandpass filter and directional coupler,it is helpful to miniaturize the microwave transceiver.The parameters of GLS unit are used to control the passband response and the level of out of band rejection,so its frequency selectivity and stopband rejection bandwidth are significantly improved.The GLS wideband filtering coupler proposed in this paper has the advantages of low loss,small size,high selectivity,wide stopband bandwidth and so on.It is an ideal choice for broadband wireless communication applications,and has important scientific significance for enriching the research system in the field of SIW filtering coupler.4.The development of modern communication system requires the dual-band performance of microwave/millimeter wave circuit.In order to improve the performance of the filtering couplers mentioned above,it’s necessary to find the method that can successfully apply the dual-band technology and multilayer technology to the design of filtering coupler.Based on the above considerations,a miniaturized multilayer dual-band filtering rat-race coupler based on the substrate integrated fan shaped cavities(SIFCs)is proposed in this paper for the first time.The dual band performance is achieved by loading a band stop resonator in the corresponding single band filtering coupler.The size of the band stop resonator is used to control the bandwidth ratio of the two passbands.The unique feature of the analysis process of the dual-band filtering coupler is that the bandwidth and center frequency of the corresponding broadband coupler can be obtained from the design specification of the dual-band filtering coupler.Generally,the proposed designs have shown excellent performance of dual-band filtering responses,isolation,amplitude balance,0° and 180° phase differences,as well as the compact structure.The proposed multilayer SIFCs dual-band filtering rat-race coupler is of great scientific significance for extending the research system of SIW filtering couplers.5.In view of the large size of the traditional SIW crossover,which is not convenient for application,this paper proposes a low loss miniaturized multilayer dual-mode SIW filtering crossover,which is mainly based on two orthogonal mode in the substrate integrated rectangular cavities(SIRCs).By properly arranging the position of the feed port and coupling slot in the multilayer SIRCs,the cross transmission and isolation response can be achieved well.Moreover,the input/output port and the isolation port can share same cavity,which save the number of resonators by two.In order to solve the problem that it is not easy to balance the isolation improvement and bandwidth expansion of traditional SIW crossover,the bandwidth of proposed design can be controlled independently in a certain range without affecting the isolation effect.With the acceptable isolation levels(>20dB),the controllable bandwidth range is from 1.1% to 6.5%.Compared with the traditional filtering crossover,its size is reduced by 85%.The proposed design based on dual-mode SIW resonator can be widely used in antenna feed network and other fields.