The analysis of a lossless helical slow-wave structure (SWS) using equivalent circuit approach, reported elsewhere, had been carried out for the fundamental mode only. This is essentially used to predict the transmission line parameters. Moreover, in the analysis the effect of permittivity on the radial propagation constant has not been considered. The radial propagation constant was considered to be same over the different structure regions. In this paper, the analysis has been developed for the space-harmonic modes considering different radial propagation constant over different structure regions. Due to it, the present analysis becomes more general, accurate and capable of dealing with a wide range of structure parameters. The dispersion relation developed here in terms of the equivalent line parameters for a lossless structure, namely, shunt capacitance per unit length and series inductance per unit length for the space-harmonic modes, as a special case, passes on to those obtained earlier by considering same radial propagation constants over different structure regions and for the fundamental mode. Besides the dispersion characteristics, characteristics impedance has also been predicted in terms of line parameters. The results presented here in terms of the structure parameters can be used for structure design and performance evaluation as well as for the control of any space harmonic of interest. The present analysis has also been validated with those experimental values reported elsewhere.
2. Ghosh, S., P. K. Jain, and B. N. Basu, "Rigorous tape analysis of inhomogeneously loaded helical slow-wave structures," IEEE Trans. on Electron Devices, Vol. 44, No. 7, 1158-1168, 1997.
3. Basu, B. N. and A. K. Sinha, "Dispersion-shaping using an inhomogeneous dielectric support for the helix in a travelling-wave tube," International Journal of Electronics, Vol. 50, 235-238, 1981.
4. Ghosh, S., P. K. Jain, and B. N. Basu, "Modified field analysis of inhomogeneously-loaded helical slow-wave structures for TWT’s," International Journal of Electronics, Vol. 81, No. 1, 101-112, 1996.
5. Sinha, A. K., R. Verma, R. K. Gupta, L. Kumar, S. N. Joshi, P. K. Jain, and B. N. Basu, "Simplified tape model of arbitrarilyloaded helical slow-wave structures of a traveling-wave tube," Proc. IEE, pt-H, Vol. 139, 347-350, 1992.
6. Ghosh, S., "Analytical studies on inhomogeneously loaded helical structures for broadband TWT’s,", Ph.D. dissertation, Dept. Electron. Eng., Banaras Hindu Univ., Varanasi, India, 1996.
7. Basu, B. N., "Equivalent circuit analysis of a dielectric-supported helix in a metal shell," Int. J. Electronics, Vol. 47, 311-314, 1979.
8. Sinha, A. K. and B. N. Basu, "Circuit parameters for a complex helical SWS combining results for simpler configuration," Indian J. Pure & Appl. Phy., Vol. 50, 235-238, 1980.
9. Kumar, L., R. S. Raju, S. N. Joshi, and B. N. Basu, "Modeling of vane-loaded slow- wave structure for broadband traveling-wave tubes," IEEE Trans. Electron Devices, Vol. 39, 1961-1965, 1992.
10. Sinha, A. K., R. Verma, Mradula, M. Kundu, R. K. Gupta, and H. N. Bandopadhyay, "Interaction structure for Gyrotrons: A study on dispersion, efficiency and cold design," Proc. of the Workshop on Gyrotron and Other Fast Wave Devices, GYROFAD-92, CEERI, Pilani, 1992.
11. Watkins, D. A., Topics in Electromagnetic Theory, John Wiley, New York, 1958.
12. Sensiper, S., "Electromagnetic wave propagation on helical structures," Proc. IRE, Vol. 43, 149-161, 1955.
13. Ghosh, S., P. K. Jain, and B. N. Basu, "Role of helix thickness in the field analysis and characterisation of the slow-wave structure of a broadband TWT," J. Inst. Electron & Telecomn. Engrs. of India, Vol. 14, No. 6, 431-438, 1997.
14. Jain, P. K., K. V. R. Murty, S. N. Joshi, and B. N. Basu, "Effect of the finite thickness of the helix wire on the characteristics of the helical slow-wave structure of a travelling-wave tubes," IEEE Trans. Electron Devices, Vol. 34, 1209-1213, 1987.
15. D’Agostino, S., F. Emma, and C. Paoloni, "Accurate analysis of helical slow-wave structures," IEEE Trans. Electron Devices, Vol. 45, 1605-1613, 1998.