Research And Design Of Miniaturized High Performance Microstrip Directional Coupler

In recent years,the Internet of Things(Io T)has become a trend of current technological development.As the most convenient data transmission method,wireless communication is widely used in data exchange between smart terminal of the Internet of Things.For high-speed and large-capacity data transmission,the RF front-end circuit has focused on broadband,miniaturization,and harmonic suppression.As the key component of microwave passive circuit,directional coupler as well as the same situation.Therefore,this dissertation takes high-performance miniaturized broadband directional coupler as the research topic,focusing on the realization of tight coupling directional coupler,the design of miniaturized multifunctional filtering coupler and broadband coupler,etc.The main content of the research is divided into the following three parts:In the first part,the various parameter matrices in the RF microwave network are introduced.With the theory of odd and even mode analysis,the generalized directional coupler is theoretically deduced and classified.Then using the theory of odd and even mode to analysis a 3d B branch-line coupler and a 3d B couple-line coupler.Finally,the related theories of coupled resonators are introduced.In the second part,a design method of the filtering coupler was analysed and introduced.meanwhile a filtering coupler based on the coplanar waveguide step impedance resonator(CPW-SIR)is proposed.Four coupled resonators are employed to replace the traditional ?/4 transmission line.By means of pairwise coupling,a filtering response on the basis of the coupler is achieved.the coupling and phase difference between the port 2 and port 3 are controlled by coupling coefficients and K-inventer,respectively.Then a new type of resonator with CPW-SIR structure is proposed,which has compact circuit size and high-order harmonic suppression.Thus a miniaturized,multi-functional high-performance directional coupler is employed.Finally,the structure of the coupler is simulated and verified.In the third part,based on multilayer slot-coupled microstrip lines,a multisection coupled line coupler is proposed.By using multilayer structure to solve the problem of loose coupling in planar couple-line.With the threecection structure which is loose coupling add tight coupling add loose coupling,a ultra-wideband frequency response is achieved.In the design of the loose coupling part,a defective ground structure(DGS)is innovatively introduced to change the even mode impedance of the couple-line as well as reduce the coupling between the couple-line on top and bottom layer.Then replace the traditional microstrip line with a narrow microstrip line structure to control the odd-mode impedance of the coupl-line,then combine the H-shaped stub to enhance the power matching of the circuit.Good amplitude and phase imbalance are obtained.Finally,the structure of this coupler is simulated and verified.