Design And Study Of Millimeter Wave Traveling Wave Tube Input And Output System

With the development of modern communication technology and military technology, traveling wave tubes are widely used in radar, electronic warfare, communications and other fields. As millimeter-wave source having a significant development prospects, millimeter wave TWT will play an increasingly important role in the field of defense and national economy. Millimeter wave TWT develops keeping the higher frequency, higher power and wider band direction, Design optimization of input and output system is one issue that must be addressed to achieve these goals. For these reasons, this paper studied input and output systems of millimeter wave TWT, and designed an input and output systems of millimeter wave TWT with the operating frequency band of 32 GHz ~ 36 GHz.The main content of this thesis is the design optimization of coupling structure with the operating frequency band of 32 GHz ~ 36 GHz.The main work and innovations are as follows:1. This paper presents two methods of rapid design of the typical coaxial window. One design method is based on the design ideas of the box-shaped window,We got the transfer matrix equivalent with the circuit diagram of typical coaxial window, and calculated initial size of coaxial window in accordance with the relationship of various parameters of the transfer matrix.The second design approach is based on the traveling wave window design idea. We calculated the initial size of the coaxial window by making the input impedance and characteristic impedance achieve to match. After comparing the theoretical and experimental values, we can prove the correctness of these two design methods. And we designed an input and output window of millimeter-wave TWT with the frequency ranging from 32 GHz to 36 GHz in accordance with this design method. Two rapid design methods of typical coaxial window provide a certain reference value for the rapid design of coaxial window.2. We compared the accuracy and applicability of two step capacitance formula. The design process of the window involves the step capacitance formula, and we found that the calculation results of the two stepped capacitance calculation method have a huge difference. But the design results of comparing the simulation when they are applied to the same window design are almost identical. So we got the conclusion that the two step capacitance calculations are both applicable to the design although there is a certain gap of them.3. Traditional quarter-wavelength impedance matching had been improved. In this article, the connecting part structure of slow wave structure and the input and output window is quarter wavelength impedance matching device. Radius of coaxial window and a spiral cross-section are not the same. In order to reduce the generation of discrete impedance, the inner conductor of impedance matching is optimized for the form of linear gradient. The entire tube simulation results show that this method to improve impedance matching structure can indeed optimize the performance of the entire transport system.4. This paper analyzed the influences of each of the key parameters on the transmission characteristics. In order to design better transmission performance of millimeter wave traveling wave tube input and output system, we scanned each of the key parameters of input and output system. At last, we designed a input and output systems of millimeter wave TWT with the operating frequency band of 32 GHz ~ 36 GHz.and its VSWR is less than 1.45.