A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is
being developed for a microwave power module (MPM) that will be used for phased
antenna array radar applications. The proposed S-band MPM provides a tenfold
peak power increase compared to state-of-the-art S-band MPMs. In this paper,
the design of the vacuum power booster TWT part of the MPM is presented. The
compact and lightweight S-band TWT is driven by a 6 kV, 0.9 A electron beam. The amplifier is predicted by
large-signal simulations to generate over 1 kW at S-band with 25 dB saturated
gain and over 40% efficiency. The stability from unwanted oscillations has been
investigated. To suppress the oscillations, the helix circuit has been coated
with carbon composite material. The coaxial input and output antennas have been
fabricated. For efficiency enhancement, a multi-stage depressed collector (MDC)
has been designed using a 3D particle-in-cell (PIC) simulator, VORPAL. The
collector design makes use of a current loop based on a feedback mechanism for
effective design process. The integrated designs of a helix circuit, an
electron gun, a periodic permanent magnet (PPM), antennas, and a collector are
presented.
References
[1]
C. R. Smith, C. M. Armstrong and J. Duthie, “The Microwave Power Module: A Versatile RF Building Block for High-Power Transmitters,” Proceedings of the IEEE, Vol. 87, No. 5, 1999, pp. 717-737.
doi:10.1109/5.757252
[2]
M. C. Smith, “Comparison of Solid State, MPM, and TWT Based Transmitters for Spaceborne Applications,” Proceedings of the IEEE Southeastcon, Orlando, 24-26 April 1998, pp. 256-259.
[3]
A. Katz, R. Gray and R. Dorval, “Performance of Microwave and Millimeter Wave Power Modules (MPMs) with Linearization,” Proceedings of the IEEE Military Communications Conference, Atlantic City, 17-20 October 2005, pp. 2693-2699. doi:10.1109/MILCOM.2005.1606073
[4]
R. J. Barker, J. H. Booske, N. C. Luhmann Jr. and G. S. Nusinovich, “Modern Microwave and Millimeter-Wave Power Electronics,” IEEE Press, Piscataway, 2005.
[5]
http://www.l-3com.com/
[6]
F. Francisco, “Private Communication,” 2009.
[7]
A. S. Gilmour Jr., “Principles of Traveling Wave Tubes,” Artech House, Norwood, 1994.
[8]
W. B. Herrmannsfeldt, “EGUN: An Electron Optics and Gun Design Program,” SLAC Report SLAC-331, Stanford, 1988.
[9]
J. R. M. Vaughan, “Synthesis of the Pierce Gun,” IEEE Transactions on Electron Devices, Vol. 28, No. 1, 1981, pp. 37-41. doi:10.1109/T-ED.1981.20279
[10]
M. Baird, “mPPM Program Manual User’s Guide,” 2002.
[11]
http://www.ansoft.com/products/em/maxwell/
[12]
C. Nieter and J. R. Cary, “VORPAL: A Versatile Plasma Simulation Code,” Journal of Computational Physics, Vol. 196, No. 2, 2004, pp. 448-473.
doi:10.1016/j.jcp.2003.11.004
