Open Yuda Zhou Dissertation.pdf - The Pennsylvania State

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Open Yuda Zhou Dissertation.pdf - The Pennsylvania State

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The Pennsylvania State University The Graduate School
Department Electrical Engineering
A STUDY OF ELECTROMAGNETIC ABSORBERS AND CLOAKS FOR THE REDUCTION OF ELECTROMAGNETIC SCATTERING
A Dissertation in Electrical Engineering
by Yuda Zhou
 2015 Yuda Zhou
Submitted in Partial Fulfillment of the Requirements for the Degree of
Doctor of Philosophy August 2015

The dissertation of Yuda Zhou was reviewed and approved* by the following:
Raj Mittra Professor of Electrical Engineering Dissertation Advisor Co-Chair of Committee
Julio Urbina Professor of Electrical Engineering Co-Chair of Committee
Ram Narayanan Professor of Electrical Engineering
Michael Lanagan Professor of Engineering Science and Mechanics
Kultegin Aydin Professor of Electrical Engineering Head of the Department of Electrical Engineering
*Signatures are on file in the Graduate School

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ABSTRACT
Electromagnetic absorbers and scattering reduction techniques have long been investigated to discover better performing configurations and exploited to reduce Radar CrossSection, act as sensors or reduce obstruction effects, throughout the electromagnetic spectrum ranging from UHF to terahertz frequencies, and even at infrared and optical wavelengths.
This dissertation presents the research on a novel interpretation and design strategy for designing absorbers based on periodic structures and introduces an algorithm for determining the optimal material parameter for layered absorbers that are wrapped around real-world objects with structural perturbations from a planar surface, which traditional research focuses on almost exclusively. A brief history of absorbers was given and legacy configurations of absorbers were introduced in the first place. Secondly, novel Frequency Selective Surface (FSS)-based absorbers were proposed based on the interpretation of the reciprocity theorem for antenna systems. FSSbased absorbers and were incorporate into layered absorbers as composites for tailored absorption specifications. A comparison of performances was given to serve as a general rule of thumb to select optimal configuration for tailored specifications. This dissertation investigates a nascent solution to the scattering reduction problem, namely cloaking based on the physics of Transformation Optics (TO) and presents the real-world limitations of such solutions. This dissertation proposes an alternative algorithm for developing the optimal material parameter for a physical object in a real-world scenario.
These explorations show the great promise and applicability of a comprehensive tailored absorber design strategy on a case-by-case basis.

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TABLE OF CONTENTS
List of Figures..........................................................................................................................vi
List of Tables ...........................................................................................................................x
Acknowledgements .................................................................................................................. xi
Chapter 1 Overview .................................................................................................................1
1.1 Dissertation Outline ...................................................................................................1 1.2 Notations and Symbols ..............................................................................................2
Chapter 2 Traditional Electromagnetic Absorbers...................................................................3
2.1 Introduction................................................................................................................3 2.2 Salisbury Screen Absorber.........................................................................................4 2.3 Dallenbach Layer Absorber .......................................................................................8 2.4 Jaumann Absorber......................................................................................................11 2.5 Summary ....................................................................................................................13
Chapter 3 Frequency Selective Surface (FSS)-based Absorber for Wideband Applications ..15
3.1 Introduction................................................................................................................15 3.2 General Reciprocity Theorem ....................................................................................16 3.3 Reciprocity Theorem for Antenna Systems ...............................................................17 3.4 Unit–Cell Design and Bandwidth Expansion.............................................................18 3.5 Wideband Unit-Cells and Dual-Direction Capabilities..............................................20 3.6 Lossy FSS Analysis ...................................................................................................22
Chapter 4 Multi-Layered Absorber for Ultra Wideband Applications ....................................28
4.1 Design of Multilayered Absorber...............................................................................28 4.1.1 Reflection Coefficient for obliquely incident stratified isotropic dielectric layers with a PEC ground plane .......................................................................28 4.1.2 Optimization Process for Maximizing Frequency Bandwidth and Minimizing Thickness......................................................................................32
4.2 RCS Reduction for Test Targets ................................................................................35 4.3 FSS and Multi-Layered Composite Absorber for Performance Enhancement ..........37
4.3.1 Target Band Absorption Enhancement ...........................................................37 4.3.2 Thickness Reduction .......................................................................................38 4.4 Summary ....................................................................................................................39
Chapter 5 Cloaking and Scattering Reduction.........................................................................41

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5.1 Introduction................................................................................................................41 5.2 Fundamentals of Transformation Optics....................................................................42 5.3 Field Transformation in the context of Generalized Scattering Matrix Approach.....52
Chapter 6 Scattering Reduction for Real-World Targets.........................................................60
6.1 Field Transformation Algorithm, Material Modification...........................................66 6.2 Field Transformation Algorithm, Thickness Modification ........................................70 6.3 Practical Applications ................................................................................................76
Chapter 7 Suggestions for Future Works.................................................................................80
Bibliography..................................................................................................................... 82

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LIST OF FIGURES
Figure.2.1. Schematics for the Salisbury screen. .....................................................................4
Figure.2.2. Wave interactions in different mediums of the Salisbury screen. .........................5
Figure.2.3. Reflection coefficients for designed Salisbury screen with different sheet resistances. .......................................................................................................................6
Figure.2.4. Reflection coefficients for designed Salisbury screen with spacers of different dielectric constants and corresponding thicknesses. ........................................................8
Figure.2.5. Schematics for the Dallenbach Layer Absorber. ...................................................9
Figure.2.6. Microwave absorption properties of the FePc–Fe3O4–BF/BPh/FePc–Fe3O4 composite laminates.........................................................................................................10
Figure.2.7. Electromagnetic properties of composite laminates: (a) real part of permittivity, (b) real part of permeability, (c) imaginary part of permittivity, (d) imaginary part of permeability.........................................................................................11
Figure.2.8. Schematics for an 8-layer Jaumann absorber. .......................................................13
Figure.2.9. Reflection coefficient for an 8-layer Jaumann absorber........................................13
Figure.3.1. Transmitting and receiving antenna systems.........................................................17
Figure.3.2. Two-antenna system with conjugate loads............................................................17
Figure.3.3. (a,d) Isometric; (b,e) top; and (c,f) side view of the cross-strip model with inter-connected resistors (red) and duo layer stack model, respectively (D=15, W=12, H=5.5, H’=11.5 unit: mm). ..................................................................................19
Figure.3.4. (a,d) Isometric; (b,e) top; and (c,f) side view of the cross-strip model with inter-connected resistors (red) and duo layer stack model, respectively (D=15, W=12, H=5.5, H’=11.5 unit: mm). ..................................................................................20
Figure.3.5. Illustration of the (a) isometric; (b) top; (c) side view of the 3-layer bowtie absorber model and the (d) 1st layer; (e) 2nd layer; (f) 3rd layer (L=53.4mm, W=21mm, d=6mm)..........................................................................................................21
Figure.3.6. Reflection, transmission and absorption coefficient of the three layer absorber-screen model. ....................................................................................................21
Figure.3.7. Schematics of the unit cell of an EM absorber based on dual-loop periodic screens, model (a). ...........................................................................................................23
Figure.3.8. Reflected power level for the original dual-loop absorber. ...................................24

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Figure.3.9. Schematics of the unit cell of a modified EM absorber utilizing lossy, complex dual-loop periodic screens, model (b). ..............................................................25
Figure.3.10. Schematics of the unit cell of a modified EM absorber based on lossy, dualloop periodic screens without segmentation, model (c)...................................................25
Figure.3.11. Reflected power level for model (b) with varying sheet resistance.....................26
Figure.3.12. Reflected power level for model (c) with varying sheet resistance.....................27
Figure.4.1. (a) TE and (b) TM wave incident obliquely on a multi-layer dielectric with a PEC ground plane. ...........................................................................................................29
Figure.4.2. Model schematics of the optimization problem for the multilayer absorber. ........33
Figure.4.3. Real and imaginary parts of the (a) permittivity and (b) permeability for the two types of absorbing materials used in the multi-layer absorbing blanket design........34
Figure.4.4. Reflection coefficient of multilayer absorber backed by a PEC plate for different number of layers................................................................................................35
Figure.4.5. Back-scattering RCS of PEC objects: (a) plate, (b) pyramid, and (c) cylinder covered with 2 and 7-layer absorbers...............................................................................36
Figure.4.6. Illustration of the (a) isometric and (b) side view of the absorber cross-strip composite model. .............................................................................................................37
Figure.4.7. Reflection coefficient of the absorber-screen composite model............................37
Figure.4.8. (a) Illustration of the broadband antenna; (b) S11 of the broadband antenna. ......38
Figure.4.9. Illustration of the (a) isometric view and (b) top view of the absorber-screen composite model. .............................................................................................................39
Figure.4.10. Reflection coefficient of the absorber-screen composite model..........................39
Figure.5.1. (a) Physical and (b) virtual domains used in the TO algorithm.............................41
Figure.5.2. (a) Schematics for a cloaked PEC cylinder with R2 = 2R1, (b) material parameters for an all-angle, all-polarization cloak, (c) material parameters for a normal-incident, TE-polarization cloak from [37]...........................................................44
Figure.5.3 TO-based cloak schematics and corresponding materials in the (a) physical geometry and (b) virtual geometry...................................................................................46
Figure.5.4 Cloak problem with mesh schematics: (a) physical and (b) virtual domains. ........47
Figure.5.5 Cloak problem with mesh schematics: (a) physical and (b) virtual domains. ........50

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Figure.5.6 Field distribution for A PEC cylinder in (a) an ideal TO cloak, (b) an ideal, thin TO cloak, (c) a 3-layered TO cloak in which the medium parameters at each layer correspond to those of the ideal thin cloak..............................................................52
Figure.5.7 Generalized Scattering Matrix (GSM) approach in the context of the Field Transformation (FT) method............................................................................................54
Figure.5.8 Scattering from an arbitrarily shaped target described in the context of Generalized Scattering Matrix (GSM) method in the physical domain (a) and virtual domain (b)........................................................................................................................57
Figure.5.9 Scattering from an FT-treated arbitrarily shaped target described in the context of Generalized Scattering Matrix (GSM) method............................................................59
Figure.6.1 Back-scattering RCS of PEC objects: (a) plate, (b) pyramid, and (c) cylinder covered with 2 and 7-layer absorbers...............................................................................61
Figure.6.2 Phase behavior of the E-field near the rectangular PEC cylinder, which is wrapped around by an absorber blanket, normally incident on the cylinder. ..................62
Figure.6.3 Phase behavior of the E-field near the rectangular PEC cylinder, which is wrapped around by an absorber blanket, for an obliquely incident plane wave. .............63
Figure.6.4 Target detection in conventional radar scenarios: mono-static and bi-static scheme [39]. .....................................................................................................................64
Figure.6.5 (a) Original 2-layer absorber wrapped around a rectangular cylinder with shape perturbation (left); (b) 2-layer absorber with TO-modified material properties around regions with the shape perturbation (left); (c) 2-layer absorber with TO modified material properties for all regions (left) and 2-layer absorber wrapped around a rectangular cylinder (right)................................................................................66
Figure.6.6 Phase behavior of scattered E-field for (a) perturbed object wrapped by blanket with original medium parameter; (b) perturbed object wrapped by blanket with locally modified medium parameter. .......................................................................68
Figure.6.7 Comparison of the amplitudes of electric fields scattered by different objects......68
Figure.6.8 Possible domain decomposition of two aircrafts: F-16 Falcon fighter jet (left) and Predator Drone UAV (right) for scattering-reduction treatment. ..............................69
Figure.6.9 Comparison of bi-static RCS for a long PEC cylinder coated with absorbers with various thickness compositions, for horizontally (up) and vertically (down) polarized illumination. .....................................................................................................71
Figure.6.10 Comparison of bi-static RCS for a PEC sphere coated with absorber with various thickness compositions........................................................................................72
Figure.6.11 Calculated and measured reflection coefficient of a five-layer absorber [40]......73

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Figure.6.12 Comparison of bi-static RCS for a PEC ellipsoid coated with absorber of various thickness compositions, under horizontally (up) and vertically (down) polarized illumination. .....................................................................................................75
Figure.6.13 Model schematics for the blockage problem: (left) side view and (right) isometric view of the victim antenna (parabolic dish) and the aggressor antenna (monopole) sharing the same platform. ...........................................................................77
Figure.6.14 Model schematics for the alternative cloak. .........................................................77
Figure.6.15 Radiation patterns for the antenna blockage problem: (blue) dish antenna, (green) dish antenna and the monopole antenna in the vicinity and (red) dish antenna with absorber-treated monopole antenna. ........................................................................78

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LIST OF TABLES
Table 2-1. Thicknesses for all the layers of the Jaumann absorber (mm)................................12 Table 2-2. Sheet resistances for all the layers of the Jaumann absorber (Ω/sq).......................12
AbsorberModelAbsorbersDissertationCylinder