Research On Microstrip Angular Log-periodic Meander Line Slow Wave Structure Traveling Wave Tube

As an important kind of vacuum electron tube that can amplify microwave signal, traveling wave tube(TWT) is widely applied in radar, communication, electronic countermeasure and other electronic equipments for their wide band width, output high power and so on. With the development of electronic technology and requirement of higher level of related equipments, high voltage and large volume for traditional traveling wave tube limits its application in many fields. Therefore, low voltage and small volume become an important research direction of the traveling wave tube.Microstrip angular log-periodic meander line slow wave structure traveling wave tube can meet the requirement of miniaturization for microstrip structure of small size and easy processing. On the other hand, the voltage is low for logarithmic spiral forming this structure, and the current is high under condition of low current density by radial sheet electron beam, which can guarantee the output power isn’t low. It provides a reference for the low voltage and miniature traveling wave tube to study and analysis for this kind of structure.Computer simulation study of microstrip angular log-periodic meander line slow wave structure is carried out by electromagnetic simulation software, the main research contents are as follows:1. Slow wave structure model set 10 log-periods is established, and then influence of microstrip line bending and structural parameters on S parameters is studied.2. Effect of structural parameters on high frequency characteristics is studied still by 10 log-periods model. The phase velocity of structure is low, in other words, its operating voltage is low, which is beneficial to low voltage operation of traveling wave tube.3. 25 periods microstrip angular log-periodic meander line slow wave structure is designed, S parameters and high frequency characteristics of slow wave structure by same and different helix growth rate are compared. Simulation study of beam-wave interaction is carried out under condition that radial uniform magnetic field produced by permanent magnet focuses electron beam. Output power of slow wave structure by different helix growth rate is higher. When 35 GHz operating frequency, 1770 V operating voltage, 0.2A current and 1W input power, output power, gain and efficiency are respectively 33.6W, 15.3dB and 9.5%, 3dB output power bandwidth is about 10 GHz. The output power decreases with the distance between electron beam and microstrip line increase.4. Based on impedance matching between microstrip and coaxial, matching coaxial to the 2.4mm standard coaxial line whose impedance is 50? transition is designed, which is taken as the input and output structure of traveling wave tubes. Simulation shows that transmission characteristics is good.