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 9, September 1998

Scattering of Electromagnetic Pulses by Simple-Shaped Targets with Radar Cross SectionModified by a Dielectric Coating

Page 1252.

Abstract:

We study the scattering interaction of electromagnetic pulses with a spherical target. The target is a perfectly conducting sphere coated with a thin dielectric layer. Two different hypothetical materials are specified: a lossy dielectric and a dielectric that also has magnetic losses. The monostatic radar cross section (RCS) is computed in each case and we examine the influence of the coating on the RCS. In particular, we compare the RCS of the coated sphere with the (normalized) backscattered power when a large perfectly conducting flat plate coated with the same dielectric layer is illuminated at normal incidence by the same waveform. In particular, we find that except for frequencies below those within the efficiency band of the absorbent material, the normalized RCS of the coated sphere agrees well with the power reflection coefficient of the plate covered with the same kind of coating. For low-frequency incidences, the peaks and dips in the RCS are more prominent for the coated target than they are for the bare one. Analyzing the response of the spherical targets in the combined time-frequency domain we demonstrate that the coating itself, although reducing the RCS could introduce additional resonance features in the target's signature at low frequencies that could be used for target recognition purposes. This observation is also confirmed by a study of the bistatic RCS of these coated objects, which we have displayed in various color graphs.

References

1. G. T. Ruck, D. E. Barrick, W. D. Stuart, and C. K. Krichbaum, Radar Cross Section Handbook.New York: Plenum, 1970, vol. 1.
2. E. F. Knott, J. F. Shaeffer, and M. T. Tuley, Radar Cross Section, 2nd ed.Norwood, MA: Artech House, 1993.
3. W. H. Press, B. P. Flannery, S. A. Teukolsky, and W. T. Vetterling, Numerical Recipes: The Art of Scientific Computing.New York: Cambridge Univ. Press, 1986.
4. A. L. Aden and M. Kerker, "Scattering of electromagnetic waves from two concentric spheres," J. Appl. Phys., vol. 22, pp. 1242-1246, Oct. 1951.
5. J. Rheinstein, "Scattering of electromagnetic waves from dielectric coated conducting spheres," IEEE Trans. Antennas Propagat., vol. 12, pp. 334-340, May 1964.
6. G. Gaunaurd, H. Überall, and P. J. Moser, "Resonances of dielectrically coated spheres and the inverse scattering problem," J. Appl. Phys., vol. 52, pp. 35-43, Jan. 1981.
7. G. C. Gaunaurd, H. C. Strifors, and W. H. Wertman, "Transient effects in the scattering of arbitrary EM pulses by dielectric spherical targets," J. Electromagn. Waves Applicat., vol. 5, pp. 75-92, Jan. 1991.
8. H. T. Kim, "High-frequency analysis of EM scattering from a conducting sphere coated with a composite material," IEEE Trans. Antennas Propagat., vol. 41, pp. 1665-1674, Dec. 1993.
9. H. C. Strifors, S. Abrahamson, B. Brusmark, and G. C. Gaunaurd, "Bistatic scattering by a spherical dielectric target illuminated by an electromagnetic pulse," in Automat. Object Recogn. III--Proc. SPIE, F. A. Sadjadi, Ed., vol. 1960, pp. 2-13, 1993.
10. H. C. Strifors, G. C. Gaunaurd, B. Brusmark, and S. Abrahamson, "Transient interactions of an EM pulse with a dielectric spherical shell," IEEE Trans. Antennas Propagat., vol. 42, pp. 453-462, Apr. 1994.
11. H. C. Strifors and G. C. Gaunaurd, "Scattering of short, ultra-wideband electromagnetic pulses by simple targets with reduced radar cross-section," in Ultra-Wideband, Short-Pulse Electromagnetics 2, L. Carin and L. B. Felsen, Eds.New York: Plenum Press, 1995, pp. 447-454.
12. L. Cohen, "Time-frequency distribution--A review," Proc. IEEE, vol. 77, pp. 941-981, July 1989.
13. --, Time-Frequency Analysis.Englewood Cliffs, NJ: Prentice-Hall, 1995.
14. T. A. C. M. Claasen and W. F. G. Mecklenbräuker, "The Wigner distribution--A tool for time-frequency signal analysis," Philips J. Res., vol. 35, pt. I, pp. 217-250; pt. II, pp. 276-300; pt. III, pp. 372-389, 1980.
15. W. J. Lentz, "Generating Bessel functions in Mie scattering calculations using continued fractions," Appl. Opt., vol. 15, pp. 668-671, Mar. 1976.
16. --, "Continuous fraction calculation of spherical Bessel functions," Comput. Phys., vol. 4, pp. 403-407, July/Aug. 1990.
17. M. Abramowitz and I. A. Stegun, Eds., Handbook of Mathematical Functions.Washington, DC: U.S. Govt. Printing Office, 1972.
18. E. M. Kennaugh and D. L. Moffatt, "Transient and impulse response approximations," Proc. IEEE, vol. 53, pp. 893-901, Aug. 1965.
19. A. V. Oppenheim and R. W. Schafer, Digital Signal Processing.Englewood Cliffs, NJ: Prentice-Hall, 1975.
20. R. E. Hiatt, K. M. Siegel, and H. Weil, "The ineffectiveness of absorbing coatings on conducting objects illuminated by long wavelength radar," Proc. IRE, vol. 48, pp. 1636-1642, 1960.
21. G. C. Gaunaurd and H. C. Strifors, "Signal analysis by means of time-frequency (Wigner-type) distributions--Applications to sonar and radar echoes," Proc. IEEE, vol. 84, pp. 1231-1248, Sept. 1996.
22. --, "Transient resonance scattering and target identification," Appl. Mech. Rev., vol. 50, pp. 131-148, Mar. 1997.
23. G. C. Gaunaurd, D. Brill, H. Huang, P. W. Moore, and H. C. Strifors, "Signal processing of the echoe-signatures returned by submerged shells insonified by dolphin "clicks": Active classification," J. Acoust. Soc. Amer., vol. 103, pp. 1547-1557, Mar. 1998 (acoustic/sonar example).