Research On High Power Millimeter Wave Quasi-Optical Power Combining Technology

With the development of science and technology,high power millimeter wave plays a more and more important role in many fields,such as information transmission,industrial production and military defense,in which various applications propose higher demand on the power sources' output level.However,limited by devices' working principle,physical structure,material performance and other factors,single power source can hardly supply enough power for some high power appliance in short millimeter wave and Terahertz bands.Therefore,power combining becomes an important solution for the problem.At present,in the high power and high frequency application scenarios,quasioptical power combiner has many advantages,such as lower power loss,higher power capacity and more branches,comparing with traditional planar power combiner and waveguide power combiner.Furthermore,phase-correcting mirror power combiner has simpler system structure and better beamforming ability than other quasi-optical power combiners.The thesis first investigates the working principles and application characteristics of two phase-correcting mirror design algorithms that are respectively used in singlemirror system and multi-mirror system.And the thesis emphatically studies the limitation that single-mirror design algorithm faces when used in multi-mirror system.On the basis of research why Gerchberg–Saxton(GS)algorithm is suitable for multimirror system designing,and combined with the advantage of Katsenelenbaum–Semenov(KS)algorithm,the thesis proposes a novel multi-mirror system design algorithm,that is the Forward and Backward Propagation(FBP)algorithm.In order to research the FBP algorithm and its designed system's properties,the thesis makes a case study of 30 GHz four-way power combiner/divider,proving the algorithm's validity in the designing of multi-mirror power combining/dividing system.Through the comparison of output results that separately come from the designed power combiner and inversely using of the designed power divider,mirror system designed by the FBP algorithm is proved to have reciprocity.The algorithm's design capability is further researched through the case of 94 GHz multi-way power divider design,which demonstrates that the algorithm keeps good design capability under different frequency conditions,and as the branch number of divider/combiner increases,the difficulty of mirror system design raises.Through the comparison of outputs coming from systems with different structure sizes and same design objective,the system structure size is proved to be a principal influence factor for the bandwidth of system output coupling degree.And through the comparison of design results obtained by the FBP algorithm and GS algorithm,it comes to a conclusion that the two algorithms have a similar multi-mirror system design capacity,and system designed by the FBP algorithm have a better bandwidth performance and its mirror is easier to utilize.Based on the aforementioned research,the thesis designs a 30 GHz high power quasi-optical power divider,and complete the device's fabrication and subsequent experimental test arrangement.Through the simulation and calculation,the device is proved to have 89.04% power transmission efficiency,93.68% coupling degree between the system's output and target field,36.67% relative bandwidth when coupling degree is higher than 85%,and power capacity of 9.986 MW.