With Cut-off Circular Waveguide Box-shaped Window

The microwave tube output window, which can be called microwave window forshort, is one important part of microwave tube. It can be used to airproof, and ensuredthe power of the microwave to output favorably. The exterior electric field on thepottery of pill-box window is weakly, so it can endure more power. And it has simplestructure, so it can be factured easily. Furthermore, its structure let it water-cooled withwater jacket, so it can be used in TWT,klystron and magnetron. In the research ofpill-box window before, it aimed at general wave-guide, that is to say, inserting a partof circular wave-guide to rectangular wave-guide, both the rectangular wave-guide andcircular wave-guide work in transmit state. There is no theory research on the pill-boxwindow, whose circular wave-guide works in cut-off state. In the dissertation, thepill-box window with circular wave-guide working in cut-off state was researched, themethod to calculate the VSWR(ρ) of it was found out, and the theoretical calculationand simulation results were in good agreement.The major achievements are listed as the followings:Introduce the theory research of general pill-box window, and improve on theinconsequence of it; Analyze the ratio of impedance of pill-box window, and compareit with experimental data, then use the method improved to calculate a lot ofρofpill-box window, and plot the theoretical calculation and simulation results which canlet us see how important the ratio of impedance, so we must choose parameters verycarefully. Plot the distribution of the field in the pill-box window.After analyzing parameters used to calculate theρ, knowing the changes of theparameters when the circular wave-guide is cut-off, and analyzing these changes' effecton the calculational formula, we found out the method to calculate theρof thepill-box window with circular wave-guide working in cut-off state. In the dissertation,we amended the equivalent susceptance to calculate the discontinuity of rectangular-to-circular wave-guide. Then we calculated theρof various sizes' pill-box windowwere in good agreement with simulation results using HFSS. Analyzing the structural parameters affectingρ, and plotting a lot of pictures, wecould choose the size with that the pill-box window would have the frequencycharacteristic.Using the method found out before to calculate pill-box window with circularwave-guide working in cut-off state, which connects normal rectangular wave-guide,the results were in good agreement with simulation results. Then we found out twobetter structures using HFSS, the one was good for of low frequency characteristic, theother was good for high frequency characteristic. Finally, we improved on the one thatwas good for high frequency, then its high frequency characteristic, and we plotted thetheoretical calculation, simulation and experiment results, they were in goodagreement.