Surface Waves
on Stealth Aircraft

Serge Y. Stroobandt

Copyright 1997–2016, licensed under Creative Commons BY-NC-SA

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Surface Waves & Stealth

Full title

The Characterization of Surface Waves
on Low-Observable Structures

being a Thesis submitted for the Degree of

Master of Science

in the University of Hull

Ing. Serge Yves Marcel Roland Stroobandt

August 1997

Highlights

Abstract

Edge diffracted waves resulting from surface discontinuities contribute significantly to the radar cross section of an object. Although this problem could be alleviated by altering the shape of the edge discontinuity, this is not always possible due to other mission requirements.

The backscatter from edge diffracted waves may also be reduced by converting the incoming radar waves into surface waves whose intensity is significantly reduced before reaching the surface discontinuity. This can be achieved by employing isotropic surface wave absorbing materials backed by a metal surface. However, for plane surface waves, the effectiveness of these materials is shown to be strongly polarization dependent.

This work suggests a new strategy which involves replacing the scattering surface by an electromagnetic soft surface. This would result in a complete elimination of the edge diffracted waves in the radar direction, independently of radar polarization.

Furthermore, a new measuring apparatus based on a partially filled rectangular waveguide has been developed for determining the attenuation constant and phase constant of plane surface waves propagating along metal-backed surface wave absorbing materials. Measurements are presented which validate this new measuring method.

Keywords

Radar Cross-Section (RCS) Management, Surface Waves, Radar Absorbing Materials, Electromagnetic Measurements

Abstract	II
Acknowledgements	V
1. Introduction	1
1.1 Stealth Design	1
1.2 Reducing the RCS Contribution of Edge Diffracted Waves	10
1.3 Outline of this Text	13
1.4 Conclusions	14
1.5 References	14
2. Hertz Potentials	15
2.1 Introduction	15
2.2 Hertz’s Wave Equation for Source Free Homogeneous Linear Isotropic Media	17
2.3 Hertz’s Wave Equation in Orthogonal Curvilinear Coordinate Systems with Two Arbitrary Scale Factors	18
2.4 Hertz’s Wave Equation in a Cartesian Coordinate System	19
2.5 Hertz’s Wave Equation for a 2D-Uniform Guiding Structure	20
2.6 Hertz’s Wave Equation in a Circular Cylindrical Coordinate System	22
2.7 Conclusions	25
2.8 References	25
3. Plane Surface Waves Along Plane Layers of Isotropic Media	26
3.1 Definition	26
3.2 Plane Surface Waves and the Brewster Angle Phenomenon	27
3.3 Plane Surface Waves, Total Reflection and Leaky Waves	28
3.4 Plane Surface Waves along a Coated, Electric Perfectly Conducting Plane	30
3.5 Plane Surface Waves along a Planar Three-Layer Structure	79
3.6 Plane Surface Waves along the Plane Interface of Two Half Spaces	91
3.7 Appendix A: The Phase Velocity of an Inhomogeneous Wave in a Loss Free Medium	95
3.8 Appendix B: Proof of \(-\text{j}\sqrt{x} = \sqrt{-x}\)	96
3.9 Conclusions	97
3.10 References	98
4. Axial Surface Waves in Isotropic Media	99
4.1 Definition	99
4.2 Axial Surface Waves along a Coated, Electric Perfectly Conducting Cylinder	100
4.3 Field Distribution of Axial Surface Waves along a Coated, Electric Perfectly Conducting Cylinder	105
4.4 Conclusions	107
4.5 References	107
5. RCS Management of Edge Diffracted Waves	108
5.1 Introduction	108
5.2 Converting the Incident Space Wave into Attenuated Surface Waves	109
5.3 Soft Surfaces	111
5.4 The Practical Realization of a Soft Surface	113
5.5 Conclusions	119
5.6 References	120
6. Surface Wave Absorber Measurements	121
6.1 Introduction	121
6.2 A Historical Overview of Surface Wave Measurement Techniques	122
6.3 A Plane Surface Wave Simulator Cell Based on a Partially Filled Rectangular Waveguide	126
6.4 Conclusions	158
6.5 References	158
7. Conclusions	159

Download the whole masterthesis in one file (10 MB PDF).

Publications

S. Y. M. R. Stroobandt and F. C. Smith, “Method for measuring the attenuation and phase constants of a surface wave propagating along an infinite plane,” Electronics Letters, 33(20):1685–1686, September 1997
F. C. Smith and S. Y. M. R. Stroobandt, “The design principles and measurement of surface wave absorbing materials,” Progress in Electromagnetics Research Symposium (PIERS) Proceedings, Volume 1, page 369, July 1998

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