The engine of a fighter plane is one of the largest scattering centers of the entire aircraft. One possible way of reducing the radar cross section (RCS) of the engine is to use an S-shaped bending air inlet to avoid direct radar wave illumination and reflection. We evaluate the efficacy of an S-shaped air inlet on RCS reduction by simulating the boresight and ±15˚ bistatic RCS for a digital model of an engine located behind an S-shaped inlet, using a multi-level fast multipole method (MLFMM) code in the S and X bands. The results show that a curved S-type air inlet can reduce the engine boresight bistatic RCS by ~10-12 dBsm at 3 GHz, and ~16 dBsm at 10 GHz when radar wave is incident from boresight, but not to the level required by RF stealth standards. When the radar waves are incident from θ=105˚ φ=90˚ or θ=90˚ φ=345˚, the RCS reduction is less effective, which is the results of the bend direction of the S-type air inlet.
Shen Shou Max Chung,
"Efficacy of an S-Shaped Air Inlet on the Reduction of Front Bistatic Radar Cross Section of a Fighter Engine," Progress In Electromagnetics Research B,
Vol. 92, 193-211, 2021. doi:10.2528/PIERB21060803
7. Crispin, Jr., J. W. and A. L. Maffett, "Estimating the radar cross section of a cavity," IEEE Trans. Aerosp. Electron. Syst., Vol. 6, No. 5, 672-674, Sept. 1970.
8. Kelly, J. D., Configuration design for low RCS, Boeing Aerospace Company 2-5173-JDK-75-068, Sept. 1975.
9. Umashankar, K., A. Taflove, and S. Rao, "Electromagnetic scattering by arbitrary shaped threedimensional homogeneous lossy dielectric objects," IEEE Trans. Antennas Propag., Vol. 34, No. 6, 758-766, Jun. 1986.
10. Chou, R. C. and S. W. Lee, "Modal attenuation in multilayered coated waveguides," IEEE Trans. Microw. Theory Techn., Vol. 36, No. 7, 1167-1176, Jul. 1988.
11. Ling, H., R.-C. Chou, and S.-W. Lee, "Shooting and bouncing rays: Calculating the RCS of an arbitrarily shaped cavity," IEEE Trans. Antennas Propag., Vol. 37, No. 2, Feb. 1989.
12. Graglia, R. D., P. L. E. Uslenghi, and R. S. Zich, "Moment method with isoparametric elements for three-dimensional anisotropic scatterers," Proc. IEEE, Vol. 77, No. 5, 750-760, May 1989.
13. Penno, R. P., G. A. Thiele, and K. M. Pasala, "Scattering from a perfectly conducting cube," Proc. IEEE, Vol. 77, No. 5, 815-823, May 1989.
14. Ruan, Y. Z. and W. L. Feng, "RCS calculation of open cavities by complex ray expansion," IEE Proc. — F, Vol. 138, No. 5, 397-399, Oct. 1991.
15. Mendes, L. and E. Arms, "TE-scattering from dense homogeneous infinite dielectric cylinders of arbitrary cross-section," IEEE Trans. on Magn., Vol. 27, No. 5, 4295-4298, Sept. 1991.
16. Hower, G. L., R. G. Olsen, J. D. Earls, and J. B. Schneider, "Inaccuracies in numerical calculation of scattering near natural frequencies of penetrable objects," IEEE Trans. Antennas Propag., Vol. 41, No. 7, 982-986, Jul. 1993.
17. Gedney, S. D., Introduction to the Finite-Difference Time Domain (FDTD) Methods for Electromagnetics, 1st Ed., Morgan & Claypool Publishers, 2011.
18. Colak, D., A. I. Nosich, and A. Altintas, "Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: The case of E-polarization," IEEE Trans. Antennas Propag., Vol. 41, No. 11, 1551-1559, Nov. 1993.
19. Colak, D., A. I. Nosich, and A. Altintas, "Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: The case of H-polarization," IEEE Trans. Antennas Propag., Vol. 43, No. 5, 440-447, May 1995.
20. Rius, J. M., A. Lozano, and A. Cardama, "RCS of engine inlets by a spectral iterative technique," 23rd European Microwave Conf., Madrid, Spain, Sept. 1993.
21. Anastassiu, H. T., J. L. Volakis, D. C. Ross, and D. Andersh, "Electromagnetic scattering from simple jet engine models," IEEE Trans. Antennas Propag., Vol. 44, No. 3, 420-421, Mar. 1996.
22. Anastassiu, H. T., Electromagnetic scattering from jet engine inlets using analytical and fast integral equation methods, Ph.D. thesis, U. of Michigan, 1997.
23. Odendaal, J. W. and D. Grygier, "RCS measurements and results of an engine-inlet system design optimization," IEEE Antennas and Propag. Mag., Vol. 42, No. 6, 16-23, Dec. 2000.
24. Hestilow, T. J., "Simple formulas for the calculation of the average physical optics RCS of a cylinder and a flat plate over a symmetric window around broadside," IEEE Antennas and Propag. Mag., Vol. 42, No. 5, 48-52, Oct. 2000.
25. Mackay, A., "Random wave and Schell model for the mean RCS of bent chaotic ducts with a homogeneous scattered aperture field distribution," IEE Proc. — Radar, Sonar Navig., Vol. 148, No. 6, 338-342, Dec. 2001.
26. Mackay, A., "Random wave methods for the prediction of the RCS of homogeneous chaotic straight ducts," IEE Proc. — Radar, Sonar Navig., Vol. 148, No. 6, 331-337, Dec. 2001.
27. Liu, J., E. Dunn, J.-M. Jin, and C. S. Liang, "Computation of radar cross section of jet engine inlets with a nonuniform cross section and complex internal structures," Proc. of IEEE Int. Sym. Ant. and Prop., San Antonio, TX, USA, Aug. 2002.
28. Anastassiu, H. T., "A review of electromagnetic scattering analysis for inlets, cavities, and open ducts," IEEE Antennas and Propag. Mag., Vol. 45, No. 6, 27-40, Dec. 2003.
29. Wong, S., E. Riseborough, G. Duff, and K. K. Chan, "Experimental facility for measuring aircraft inlet/engine radar cross section," RTO-MP-SET-080, Oslo, Norway, Oct. 11–13, 2004.
30. Wong, S. K., E. Riseborough, G. Duff, and K. K. Chan, "Radar cross-section measurements of a full-scale aircraft duct/engine structure," IEEE Trans. Antennas Propag., Vol. 54, No. 8, 2436-2441, Aug. 2006.
31. Burkholder, R. J. and T. Lundin, "Forward-backward iterative physical optics algorithm for computing the RCS of open-ended cavities," IEEE Trans. Antennas Propag., Vol. 53, No. 2, 793-799, Feb. 2005.
32. Chan, K. K., S. K.Wong, and E. S. Riseborough, "Radar cross section modeling and measurements of inlets and cylinders with skew blades," IEEE Trans. Antennas Propag., Vol. 54, No. 10, 2930-2939, Oct. 2006.
33. Poyatos-Martınez, D., D. Escot-Bocanegra, R. Fernandez-Recio, and I. Montiel-Sanchez, "RCS analysis of a configurable mock-up cavity with blade motion capability," IEEE Trans. on Magn., Vol. 45, No. 3, 1096-1099, Mar. 2009.
34. Van Der Ven, H. and H. Schippers, "High range resolution profiles for a civilian aircraft inlet," NLR-TP-2010-527, National Aerospace Laboratory NLR, Feb. 2011.
35. Miacci, M. A. S. and M. C. Rezende, "Basics on radar cross section reduction measurements of simple and complex targets using microwave absorbers," Applied Measurement Systems, Z. Haq (ed.), InTech, Ch. 16, 351-376, Feb. 2012.
36. Wang, L., Y.-C. Zhong, and K.-Y. Zhang, "Electromagnetic scattering study for metal/dielectric coated inlet diffuser," Acta Phys. Sin., Vol. 61, No. 23, 234101, 2012 (in Chinese).
37. Mo, J., W. Fang, H. Xue, Y. Yan, and Z. Ma, "Accurate evaluation of RCS on the structure of aircraft Inlets," Proc. of Int. Sym. Ant. Prop. (ISAP) 2013, Nanjing, China, Oct. 2013.
38. Kim, Y. D., H. Lim, J. H. Han, W. Y. Song, and N. H. Myung, "RCS reduction of open-ended circular waveguide cavity with corrugations using mode matching and scattering matrix analysis," Progress In Electromagnetics Research, Vol. 146, 57-69, 2014.
39. Vogel, M., "Radar cross section of aircraft with engine inlets including fan blades," Proc. of Int. Sym. on Ant. Prop. (APSURSI), Fajardo, Puerto Rico, Jun. 26–Jul. 1, 2016.
40. Song, J., C.-C. Lu, and W. C. Chew, "Multilevel fast multipole algorithm for electromagnetic scattering by large complex objects," IEEE Trans. Antennas Propag., Vol. 45, No. 10, 1488-1493, Oct. 1997.
41. Ai, J.-C., L. Chou, and C.-J. Yang, S-bend Stealth Inlet, Defense Industry Pub., ISBN 978-7-118-11082-1, 2017 (in Chinese).
42. Naval Air Warfare Center Weapons Division, Electronic Warfare and Radar Systems Engineering Handbook, 4th Ed., NAWCWD TP 8347, 2013.
43. Chung, S. S. M., "Ch. 1: Manipulation of radar cross sections with plasma," Radar Systems: Technology, Principles and Applications, 1-44, Wen-Qin Wang (Ed.), Nova Science Pub. Inc., UK, May 17, 2013.
44. Dynamical Range of a Receiver, [Online], , Available: https://www.radartutorial.eu/09.receivers/rx-52.en.html.
45. Tuan, S.-C. and S. S. M. Chung, "Radar cross section and near field of an engine digital mock-up under UHF and S band radar illumination," EuRad2018, European Microwave Week (EuMW2018), Ifema Feria De Madrid, Spain, Sept. 23–28, 2018.
46. Chung, S. S. M., "Parametric simulation on reduction of S-band rear bistatic radar cross section of jet engine with vector thrust nozzle via plasmatized exhaust," IEEE Trans. Plasma Sci., Vol. 45, No. 3, 388-404, Jan. 31, 2017.
55. Matrix representation of Maxwell's equations, [Online], , Available: https://en.wikipedia.org/wiki/Matrix_representation_of_Maxwell%27s_equations.
56. Basic Principle of the Method of Moments, [Online], , Available: http://www.emagtech.com/wiki/index.php/Basic_Principles_of_The_Method_of_Moments.
57. Chew, W. C., J.-M. Jin, E. Michielssen, and J. Song, Algorithms in Computational Electromagnetic, Artech House, 2001.
58. Alves, M. A., I. M. Martins, M. A. S. Miacci, and M. C. Rezende, "Radar cross section of simple and complex targets in the C-band: A comparison between anechoic chamber measurements and simulations," PIERS Online, Vol. 4, No. 7, 791-794, 2008.
59. Boeing T-X Trainer Aircraft, [Online], , Available: https://www.airforce-technology.com/projects/boeing-t-x-trainer-aircraft/.