1998 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

IEEE Transactions on Antennas and Propagation
Volume 46 Number 10, October 1998

Table of Contents for this issue

Complete paper in PDF format

Incremental Length Diffraction Coefficients for the Shadow Boundary of a Convex Cylinder

Thorkild B. Hansen, Member, IEEE, and Robert A. Shore, Senior Member, IEEE

Page 1458.

Abstract:

Incremental length diffraction coefficients (ILDC's) are obtained for the shadow boundaries of perfectly electrically conducting (PEC) convex cylinders of general cross section. A two-step procedure is used. First, the nonuniform (NU) current in the vicinity of the shadow boundary is approximated using Fock functions. The product of the approximated current and the free-space Green's function is then integrated on a differential strip of the cylinder surface transverse to the shadow boundary to obtain the ILDC's. This integration is performed in closed form by employing quadratic polynomial approximations for the amplitude and unwrapped phase of the integrand. Examples are given of both the current approximations and the integration procedure. Finally, as an example, the scattered far field of a PEC sphere is obtained by adding the integral of the NU ILDC's of a circular cylinder along the shadow boundary of the sphere to the physical optics (PO) far field of the sphere. This correction to the PO field is shown to significantly improve upon the accuracy of the PO far-field approximation to the total scattered field of the sphere.

References

  1. P. Y. Ufimtsev, Method of Edge Waves in the Physical Theory of Diffraction.Moscow, Russia: Sovyetskoye Radio, 1962 (Engl. transl. available from Nat. Tech. Inform. Serv., Springfield, VA 22161 USA; #AD733203.)
  2. K. M. Mitzner, Incremental Length Diffraction Coefficients, Tech. Rep. no. AFAL-TR-73-296, Apr. 1974 (available Nat. Tech. Inform. Serv., Springfield VA 22161 USA; #AD918861).
  3. A. Michaeli, "Equivalent edge currents for arbitrary aspects of observation," IEEE Trans. Antennas Propagat., vol. AP-32, pp. 252-258, Mar. 1984; Corrections IEEE Trans. Antennas Propagat., vol. AP-33, p. 227, Feb. 1985.
  4. E. F. Knott, "The relationship between Mitzner's ILDC and Michaeli's equivalent currents," IEEE Trans. Antennas Propagat., vol. AP-33, pp. 112-114, Jan. 1985.
  5. R. A. Shore and A. D. Yaghjian, "Incremental diffraction coefficients for planar surfaces," IEEE Trans. Antennas Propagat., vol. 36, pp. 55-70, Jan. 1988; Corrections IEEE Trans. Antennas Propagat., vol. 37, p. 1342, Oct. 1989.
  6. A. D. Yaghjian, R. A. Shore, and M. B. Woodworth, "Shadow boundary incremental length diffraction coefficients for perfectly conducting smooth, convex surfaces," Radio Sci., vol. 31, pp. 1681-1695, Nov./Dec. 1996.
  7. T. B. Hansen and A. D. Yaghjian, "Incremental diffraction coefficients for cylinders of arbitrary cross section: Application to diffraction from ridges and channels in perfectly conducting surfaces," in IEEE Antennas Propagat. Soc. Symp. Dig., Univ. Western Ontario, London, ON, Canada, June 1991, pp. 794-797.
  8. R. A. Shore and A. D. Yaghjian, "A comparison of two incremental diffraction coefficients for convex perfectly electrically conducting cylinders," in Int. Symp. Electromagn. Theory, Int. Union Radio Sci. (URSI), Aristotle Univ., Thessaloniki, Greece, May 1998, pp. 4-6.
  9. V. A. Fock, Electromagnetic Diffraction and Propagation Problems.Oxford, U.K.: Pergamon, 1965.
  10. L. N. Medgyesi-Mitschang and D. L. Wang, "Hybrid solutions for scattering from perfectly conducting bodies of revolution," IEEE Trans. Antennas Propagat., vol. AP-31, pp. 570-583, July 1983.
  11. G. T. Ruch, Ed., Radar Cross Section Handbook.New York: Plenum, 1970, vol. 1.
  12. D. P. Bouche, F. A. Molinet, and R. Mittra, "Asymptotic and hybrid techniques for electromagnetic scattering," Proc. IEEE, vol. 81, pp. 1658-1684, Dec. 1993.
  13. T. B. Hansen and R. A. Shore, "The currents on a cylinder illuminated by a general plane wave," IEEE Trans. Antennas Propagat., vol. 43, pp. 1464-1465, Dec. 1995.
  14. --, "Incremental length diffraction coefficients for the shadow boundary of a general cylinder," Rome Lab. Rep. RL-TR-97-151, July 1997.
  15. J. J. Bowman, T. B. A. Senior, and P. L. E. Uslenghi, Electromagnetic and Acoustic Scattering by Simple Shapes.Amsterdam, The Netherlands: North-Holland, 1969.
  16. M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions.New York: Dover, 1972 (9th printing).
  17. W. H. Press, S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, Numerical Recipes in Fortran.New York: Oxford Univ. Press, 1992.