Study On The Design Of High-performance Microwave Passive Devices With Planar Discrete Structures

Over the years,miniaturization and high-performance design have been the pursuit of microwave passive device design,and significant progress has been made in materials,processes and structural design.In general,after the breakthrough of materials and processes,the circuit structural design of microwave passive devices becomes the focus.Therefore,a fundamental problem faced in the design of high-performance microwave passive devices is that to achieve a certain type of passive devices in the condition of the given materials,processes and circuit design space,what kind of structure can provide the best performance?Most of the existing circuit structure design methods are based on the "cut-and-try and optimize" design pattern,which has certain limitations.Therefore,achieving the optimal circuit structure design with the best performance and flexible configuration requires the use of more efficient structure description and optimization techniques.In this dissertation,the multi-objective evolutionary algorithm based on decomposition(MOEA/D)is used as an optimization framework to design the planar discrete circuit structure,so as to achieve high-performance microwave passive device design.Focusing on the discrete circuit structure design,the research contents include:1.The design method based on discrete structure is proposed and the discrete structure related characteristics are studied.The dissertation uses the idea of discretization to describe the circuit structure,which can break the topology or shape of the conventional circuit.As the discrete structure is different from the conventional regular structure,an approximate equivalent circuit analysis method is applied to study its characteristics of loss,wideband and miniaturization.2.High-efficiency searching strategies and methods for discrete structures are proposed.In this dissertation,MOEA/D combined with genetic operators(MOEA/D-GO)is used as an optimized kernel to solve the discrete structure optimization problem.In order to speed up the design efficiency,the engineering experience related to microwave passive device design is integrated into MOEA/D-GO to solve the multi-objective optimization problem(MOP)of discrete microwave passive devices.On this basis,several kinds of high-efficiency searching strategies and methods are proposed.3.Planar discrete structure are used for the first time in the design of mircostrip directional coupler.The lossless and lossy S-parameters constraints of directional coupler are analyzed,which clarifies the aims of the optimization search of discrete structure.On this basis,a series of high-performance directional couplers based on planar discrete structure are implemented in combination with aforementioned high-efficiency searching strategies.The overall performance of these designs are significantly better than the previously reported design results.4.The designs and applications of planar discrete structures in high-performance filters are studied.In this dissertation,the discrete coupling structure is used to replace the partial coupling structure in the original filter to achieve high-performance filter design,which intuitively demonstrates the benefits of the discrete structure in filter design application.On this basis,a fully discrete filter and balun filter is further designed.The comparison of design efficiency under different optimization searching strategies is summarized.5.Planar discrete structures are used for multiple-input multiple-output antennas isolation design.The decoupling principle of discrete structure is briefly introduced and three high isolation MIMO antennas are designed.The influences of the discrete isolation structure on the performance of the MIMO antennas are discussed.Besides,some aspects related to the discrete structure such as cell size,design space,and density of metal cells are also discussed.In summary,focusing on the design of the circuit structure in the condition of the given materials,processes,and design space,a novel and efficient design technique for the design of high-performance microwave passive devices with good structural adaptability is provided by using the effective planar discrete structure description and multi-objective optimization technique.