The open rectangular grating with step-loaded slow-wave structure (SWS), a type of all-metal SWS for high power wide band mm-wave wave traveling wave tubes (TWT) is presented in this paper. By using the jumping conditions at the interface of two neighboring steps and single-mode approximation (SMA) field matching theory, the dispersion equation and coupling impedance of this SWS were obtained. Then the obtained complex dispersion equation was numerically calculated, and the slow-wave characteristics of the fundamental wave of this structure were discussed. Moreover, the calculation results by our theory were accordant with the simulation data obtained by the 3-D electromagnetic simulation software HFSS, The numerical calculation results show that the dispersion characteristics and coupling impedance are notably improved by loading the steps. And the working bandwidth may be the widest when the thickness of the step is about equal to the thickness of the groove depth. The proper design parameters can be optimized to meet the needs of high frequency characteristics with wide bandwidth and high output power. The present study will be useful for further research and design of this kind of high frequency system.
2. Kory, C., et al., "Novel TWT interaction circuits for high frequency application," International Vacuum Electron Conference 2004, 51-52, 2004.
3. Louis, L. J., J. E. Scharer, and J. H. Booske, "Collective single pass gain in a tunable rectangular grating amplifier," Physics of Plasmas, Vol. 5, No. 5, 2797-2805, 1998.
4. Collin, R. E., Foundations for Microwave Engineering, 2nd Ed., 571-580, Wiley-IEEE Press, New York, 2001.
5. Maragos, A. A., Z. C. Ioannidis, and I. G. Tigelis, "Dispersion characteristics of a rectangular waveguide grating," IEEE Trans. on Plasma Science, Vol. 31, No. 3, 1075-1082, 2003.
6. Gong, Y.-B., et al., "Study on mm-wave rectangular grating traveling wave tube with sheet-beam," J. Infrared Millim. Waves, Vol. 25, No. 3, 173-178, 2006.
7. Lu, Z.-G., et al., "Study on step-loaded rectangular waveguide grating slow-wave system," J. Infrared Millim. Waves, Vol. 25, No. 3, 349-354, 2006.
8. Yue, L., et al., "Analysis of coaxial ridged disk-loaded slow-wave structures for relativistic traveling wave tubes," IEEE Trans. on Plasma Science, Vol. 32, No. 3, 1086-1092, 2004.
9. Wang, W. X., G. F. Yu, and Y. Y.Wei, "Study of the ridge-loaded helical groove slow-wave structure," IEEE Trans. Microwave Theory Tech., Vol. 45, No. 8, 1689-1695, 1997.
10. Ramo, S., J. Whinnery, and T. V. Duzer, Fields and Waves in Communication Electronics, 573-579, Wiley, New York, 1965.
11. Liao, M.-L., et al., "Study on mm band open rectangular waveguide grating," The 17th Annual Seminar Conference on Military Microwave Tube, 272-276, The Chinese Electronic Society, Yichang, 2009.
12. Liu, S.-G., Introduction of Microwave Electronics, 234-246, National Defence Industry Press, Beijing, 1985.