The Investigation On Compact Combiner With High Power Density

With the development of electronics and information technology,series of military and commercial scenarios of high power RF/microwave application emerged.As a diversity technique,Power Combining shows a high potential for obtaining kilowatt output in a full solid-state system with compact volume and lower systematic complexity.The previous researches on power combiner concerning less in high power capacity,high efficiency,high isolation and miniaturization simultaneously,in this dissertation,thesis is all around compact combiner with high power density.The main researches are summarized as follow.The S parameter of multiport microwave device is analyzed at first,and S matrix of an ideal equipower combiner with its degree of freedom is derived.Common-used circuits'topologies and structures are demonstrated and analyzed by odd-and even-mode theory.We proposed a novel combining topology of constant characteristic impedance applied to cavity-based combiner,which overcomes the dilemma of input/output matching and isolation controlled by variation of the same transmission line.The major line in it is homogeneous without any abrupt steps,implying the high convenience for high power application.A quick method for calculating the efficiency of combiner is proposed.Meanwhile,the failure analysis,especially the sparking phenomenon in cavity is investigated.The research indicate that Paschen's law and Kilpatrick limit are applied to different environment from vacuum to high pressure.From Paschen sparking voltage formula,we derived an approach for estimating the breakdown field in atmosphere for microwave band.The micro-coaxial high-power multiway combiner and the corresponding designing method are investigated.Mainly designed,simulated,fabricated and measured two compact combiners(two-ways and four-ways)and three super-compact combiners(two-ways and four-ways)based on micro-coaxial structure in X band.Finally,the miniaturized combiners bearing kilowatt pulse power with the dimension in a wavelength are achieved.In the final part,we investigate the cavity-based high power combiner and the corresponding design method.Mainly designed a radial combiner with to-ground-step probe excitation,rounded square compact combiner and the high isolation version.For a passive combiner,the designate power density can be over than 100W/mm~3 with the volume less than a wavelength cube.On the basis above,by employing an isolation circuit embedded directly on the output ports,performances of combiner are highly promoted,where the input and output can together be matched and isolation exceeded20dB simultaneously.