Research On H-Plane Full-band Quasi-Planar Waveguide Magic-T

In microwave passive circuits,waveguide magic-Ts have various functions,one of which is typically used as a power combiner.Different from two-way T-type waveguide power combiner,the waveguide magic-T can provide the stabilized power combining due to the high isolation between its input ports,which effectively reduces the interference between input ports.Conventional waveguide magic-Ts have large volume and must introduce extra matching elements such as metal cylinders,metal cones,and metal irises,etc.It is difficult to guarantee the machining accuracy of these matching elements.In addition,split-block machining technology must be used to fabricate the magic-T.When the multi-block structure of the magic-T is assembled,it is easy to introduce additional assembly errors.Hence,in order to overcome these shortcomings,this thesis designs compact,broad bandwidth and easy-processing waveguide magic-Ts.The main work of this thesis is summarized as following:1.Three-port network and four-port network are introduced.The structure and working principle of the waveguide E-T junction,waveguide H-T junction and waveguide magic-T are analyzed.2.The design process of H-plane full-band waveguide magic-T is introduced.The design process mainly consists of two parts,one is the design of magic-T with a nonstandard port,and the other is design of ridge waveguide transition.Then,two parts are combined and optimized to achieve the final full-bandwidth magic-T.Finally,the fullbandwidth magic-T was fabricated and measured,which validates the design structure.3.Based on the design concept of the H-plane full-band waveguide magic-T,a Hplane ultra-wideband magic-T is designed.The magic-T is used for the power dividing/combining and its different port is used as a matching port.By cascading three ultra-wideband magic-Ts,a four-way power divider/combiner is designed.Finally,the ultra-wideband magic-T was fabricated and measured and simulated results are in agreement with the measured results.4.An ultra-wideband single-ridge waveguide to coaxial line transition is designed,which uses matching network and short circuit to achieve broadband performance.The whole structure of the transition is very simple and can be readily fabricated with a conventional CNC machine.The transition was fabricated and measured.The measured results show that in the frequency range from 6-18 GHz,the return loss of the single transition is higher than 23 dB and the return loss and insertion loss of the back-to-back transition are better than 18 dB and 0.2 dB,respectively.Finally,all work of this thesis is summarized.