Research On Millimeter-Wave/Terahertz Power Combining Technologies

In recent years,great progress has been made in the millimeter-wave/terahertz fields such as communication and radar.However,the lack of low-cost,compact power source limits the application of the millimeter-wave/terahertz system.To overcome this problem,the need for the power-combining technologies becomes a good choice for the high power level.Both the waveguide-based spatial power-dividing/combining circuits and quasi-optical power-dividing/combining circuits attract more and more attentions because of the advantages of the low loss,high power-handling capability,high power-combining efficiency and multiway compared with the conventional planar power-combining circuits at the millimeter-wave/THz frequencies.In this dissertation,several novel three-dimensional(3D)and quasi-two-dimensional(quasi-2D)quasi-optical power-dividing/combining circuits including the optimization algorithm,and several all-metal waveguide power-dividing/combining circuits have been presented.The theoretical modeling method,calculation and simulation,and experimental analysis have been studied.The main contents are studied as follows:1.A swarm intelligent optimization algorithm is presented to finish the optimization in the shape designing of the 3D and quasi-2D quasi-optical power-dividing/combining circuits.The proposed algorithm is called RGA-DE algorithm.The RGA-DE is created by the study of the evolutionary process of some species.By using the elitist selection and differential evolution operator in the RGA-DE,a better searching ability is obtained in a small number of individuals.A common quasi-optical power-combining circuit is introduced to describe the code mode,interpolation,mutation,fitness and optimization results of the RGA-DE algorithm.The comparison with the conventional real-coding genetic algorithm has also been given to display the advantage of the RGA-DE algorithm optimizing the quasi-optical power combining circuit.This will lay the foundation for the designing the of the various millimeter-wave/THz quasi-optical power combining circuits.2.Both a power combiner based on 2D simple periodic hole-shaped grating and a shaped-hologram power combiner for the high power-combining efficiency are proposed.The holograms can be regarded as diffractive phase elements that only change the phase of the beam wave radiated from the horn antenna array.The beam wave reconstructed by the hologram is focused on the receiving horn antenna by the shaped reflector to obtain good performance.The design method of the shaped hologram is displayed in this dissertation.In addition,the power dividing/combining circuits with only one or two metal shaped reflectors are also studied.3.For the first time,a 2D scalar diffraction theory including the analytic expression has been proposed.A 2D electromagnetic model is built to solve a specific 3D problem.The proposed method avoids the needs for large computer resources and the time-consuming in solving the problem of the electrically large size parallel-plate cavity.A 3D model is built in 3D full-wave electromagnetic simulation sofware HFSS.By comparing the results based on the 2D scalar diffraction theory with the 3D full-wave electromagnetic simulation ones based on the finite element method,the 2D scalar diffraction theory is proven to be effective to obtain the diffraction field in the parallel-plate cavity.4.Firstly,several novel quasi-optical power dividing/combining circuits with shaped reflector in a parallel-plate cavity are presented.Based on the proposed 2D scalar diffraction theory,different receiving field distributions are obtained by the RGA-DE algorithm.The H-plane horn antenna array and the gap waveguide transition are used to receive energy in different quasi-optical power dividing/combining circuits,respectively.The design method improves the magnitude and phase balance of the quasi-optical power divider greatly.In additional,based on the proposed 2D scalar diffraction theory,a Ka-band SIW power divider and a W-band power divider with two shaped holograms are proposed with the detailed design procedure.5.Two all-metal-waveguide power dividers are presented based on the improved H-plane T-junction.Another all-metal-waveguide radial power divider with different matching elements is also studied.The simulated theoretical power-handling capacity of the radial power divider at different frequencies is obtained.In additional,spoof surface plasmon polariton(SSPP)has been given a further study.The transition from rectangular waveguide to SSPP is presented,and the performance of the SSPP at THz is shown based on simulation method.The H-plane Y-junction is achieved using two-sided corrugated waveguide with low insertion loss.