High-Frequency Characteristics of the Axisymmetric TM Modes in a Coaxial Staggered Double-Grating Slow-Wave Structure

摘要

The formulas of dispersion and interaction impedances of the axisymmetric TM modes in a coaxial double-grating slow-wave structure (SWS) are obtained utilizing the field matching method, in which the higher order terms of the field in the grooves have been considered. The high-frequency characteristics of lowest two modes—the fundamental mode and the TM mode—in the SWS were discussed by adjusting its structure parameters. The calculated results show that the dispersion curve and the interaction impedance are in good agreement with those simulated by the CST-MWS code. In addition, the parameter analysis demonstrates that the rational selection of the position of the beam tunnel and the relative position of the upper and lower gratings are helpful for the development of the traveling-wave tube and the back-wave oscillator to improve the bandwidth and enhance the interaction impedance.