The design, analysis, and manufacturing of an oversized circular metallic corrugated waveguide with rectangular and square grooves for transmitting power from gyrotron to tokamak or dummy load have been carried out. To carry high power at millimeter wave with lower transmission loss, a corrugated waveguide is preferred. A corrugated waveguide with HE11 mode gives lower attenuation than a smooth circular waveguide with TE11 mode. The theory behind the depth and width selection of corrugations required to carry the linearly polarized (HE11) mode is explained in this paper. The proposed structures are designed and simulated in CST microwave studio software. Rectangular and square groove circular corrugated waveguides each having a length of 500\,mm were fabricated and tested using ZVA50 vector network analyzer. Based on the performance results, it is derived that the square groove corrugated waveguide gives lower insertion loss of 0.08 dB/meter than rectangular groove corrugated waveguide which gives insertion loss of 0.11 dB/meter.
1. Singha, U., N. Kumara, H. Khatuna, N. Kumara, V. Yadava, A. Kumara, M. Sharmaa, M. Alariaa, A. Beraa, P. K. Jain, and A. K. Sinhaa, "Design of 42GHz gyrotron for Indian fusion tokamak system," Fusion Engineering and Design, Vol. 88, No. 11, 2898-2906, November 2013. doi:10.1016/j.fusengdes.2013.06.001
2. Doane, J. L. and C. P. Moeller, "HE11 mitre bends and gaps in a circular corrugated waveguide," International Journal of Electronics, Vol. 77, No. 4, 489-509, 1994. doi:10.1080/00207219408926081
3. Kowalski, E. J., "Miter bend loss and higher order mode content measurements in overmoded millimeter-wave transmission lines,", Ph.D. diss., Massachusetts Institute of Technology, 2010.
4. Doane, J. L., "Mode converters for generating the HE11 (Gaussian-like) mode from TE01 in a circular waveguide," International Journal of Electronics Theoretical and Experimental, Vol. 53, No. 6, 573-585, 1985. doi:10.1080/00207218208901551
5. Doane, J. L., "Design of circular corrugated waveguides to transmit millimeter waves at ITER," Fusion Science and Technology, Vol. 53, No. 1, 159-173, 2008. doi:10.13182/FST08-A1662
6. Kiran, D. V., D. S. Narayanan, V. K. Killamsetty, and B. Mukherjee, "Photonic waveguide inspired corrugated cross-coupled notch DRA," Electromagnetics, Vol. 38, No. 7, 458-468, 2018. doi:10.1080/02726343.2018.1519160
7. Clarricoats, P. J. B. and P. K. Saha, "Attenuation in corrugated circular waveguide," Electronics Letters, Vol. 6, No. 12, 370-372, 1970. doi:10.1049/el:19700260
8. Clarricoats, P. J. and A. D. Olver, "Low attenuation in corrugated circular waveguides," Electronics Letters, Vol. 9, No. 16, 376-377, 1973. doi:10.1049/el:19730278
9. Clarricoats, P. J. B. and P. K. Saha, "Propagation and radiation behaviour of corrugated feeds Part I — Corrugated waveguide feed," Proceedings of the Institution of Electrical Engineers, Vol. 118, No. 9, 1167-1176, September 1971. doi:10.1049/piee.1971.0211
10. Vallinas, J. T., "Modern corrugated horn antennas,", Ph.D. Thesis, Universidad P´ublica de Navarra, Pamplona, 2003.
11. Doane, J. L., "Propagation and mode coupling in corrugated and smooth-wall circular wavguides," Journal of Infrared and Millimeter Wave, Vol. 13, 123-170, 1985.
12. Thumm, M., "Design of short high-power TE11-HE11 mode converters in highly overmoded corrugated waveguides," IEEE Transactions on Microwave Theory and Techniques, Vol. 39, 301-309, February 1991. doi:10.1109/22.102974
13. Olver, A. D., "Corrugated horns," Journal of Electronics and Communication, Vol. 1, No. 4, 4-10, February 1992.
14. Doane, J. L., Overmoded Waveguide Components for the ECH System on PDX, No. PPPL-2071, Plasma Physics Lab, Princeton Univ., NJ, USA, 1984.
15. Nanni, E. A., S. K. Jawla, M. A. Shapiro, P. P. Woskov, and R. J. Temkin, "Low-loss transmission lines for high-power terahertz radiation," Journal of Infrared, Millimeter and Terahertz Waves, Vol. 33, No. 7, 695-714, July 2012. doi:10.1007/s10762-012-9870-5
16. Fiedziuszko, S. J. and G. A. Fiedziuszko, "Flexible waveguide with rounded corrugations,", U.S. Patent 6,559,742, issued May 6, 2003.
17. Patel, A., R. Goswami, K. Mahant, P. Bhatt, H. Mewada, A. Vala, K. Sathyanarayan, and S. Kulkarni, "Millimeter-wave TE01-TE11-HE11 mode converter using overmoded circular waveguide," Journal of Electromagnetic Wave and Applications, Vol. 32, No. 14, 2018. doi:10.1080/09205071.2018.1468286
18. Patel, A., R. Goswami, and P. Bhatt, "TM11 to HE11 mode converter in overmoded circular corrugated waveguide," IET Antenna and Microwave Propagation, Vol. 3, No. 8, 1202-1207, 2019. doi:10.1049/iet-map.2018.5627
19. Sathyanarayana, K., S. V. Kulkarni, A. Patel, P. Bhatt, A. Vala, H. Mewada, and K. Mahant, "Sensitivity analysis on predicted microwave performance of mode converters with geometrical tolerances for 42-GHz transmission line components," Fusion Science and Technology, Vol. 75, No. 3, 234-243, 2019. doi:10.1080/15361055.2018.1557984