Zigzag Lines Used In Microwave Tubes Microstrip Slow-wave Structure Theory

Microwave tubes are a kind of vacuum electron devices, which have been widely used in radar system, electronic countermeasure and satellite communication with its high power and high frequency. A slow-wave structure is an important component of traveling-wave tubes, where electromagnetic wave interacts with electron beams. The growth of the communications industry has imposed a demand for high frequency and microscale. Recent development in microfabrication has provided new opportunities for fabricating micro-vacuum electron devices, especially with microstrip meander-line slow-wave structure.With the development of software technology and the improvement of computer performance, computer simulation technology has been widely applied in the research of microwave tubes. Assisted by some essential experiments, the Computer Aided Design technology brings some benefits in research and development process, which result in major savings in development time and cost.Based on the theory of J. A. Weiss, the mechanism of meander-line slow-wave structure is presented in this thesis. The cold characteristics such as dispersion, coupling impedance and attenuation were analyzed and the dispersion equation deduced by the multi-conductor method. The results showed a good agreement with simulation values.Using electromagnetic simulation codes MAFIA and Microwave Studio, simulation of dispersion characteristics and coupling impedance of the microstrip meander-line slow-wave structure was carried out, followed by the analysis of S parameter and attenuation according to their expressions. The results showed high slope of dispersion and poor transmission in higher frequency. Additionally, the effects of different geometric parameters on dispersion were discussed, and the dispersion characteristic can be improved by changing the thickness of substrate and the width of microstrip with fixed periodic length. For microstrips in millimeter size, the dispersion curves become flatter and improved dramatically. Furthermore meander-line structure supported by dielectric slab was analyzed, which raised the resonant frequency but didn't improve the dispersion. Finally, vane-loaded waveguide slow-wave structure was studied, which demonstrated it can be used in microwave devices with high power and wide...