Friday, April 10, 2015

Metamaterials for Radars and RCS Reduction

Metamaterials Commercialization Center | Another Idea from Intellectual Ventures
Metamaterials are an innovative means of precisely controlling electromagnetic or acoustic waves as they travel through a propagating medium.  For more than a decade, The Invention Science Fund has been working in the metamaterials field with its own inventors, as well as through collaborations with pioneer academic researchers.  In 2013, ISF established the Metamaterials Commercialization Center to propel the development and commercial readiness of disruptive new metamaterials-based products for markets ranging from communications and radar to imaging and acoustics.

Books

Wiley: Metamaterials with Negative Parameters: Theory, Design and Microwave Applications - Ricardo Marqués, Ferran Martín, Mario Sorolla
The first general textbook to offer a complete overview of metamaterial theory and its microwave applications
Metamaterials with Negative Parameters represents the only unified treatment of metamaterials available in one convenient book. Devoted mainly to metamaterials that can be characterized by a negative effective permittivity and/or permeability, the book includes a wide overview of the most important topics, scientific fundamentals, and technical applications of metamaterials.
Chapter coverage includes: the electrodynamics of left-handed media, synthesis of bulk metamaterials, synthesis of metamaterials in planar technology, microwave applications of metamaterial concepts, and advanced and related topics, including SRR- and CSRR-based admittance surfaces, magneto- and electro-inductive waves, and sub-diffraction imaging devices. A list of problems and references is included at the end of each chapter, and a bibliography offers a complete, up-to-date representation of the current state of the art in metamaterials.

Links to Amazon Books

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Antenna Lenses

Metamaterial Radar May Improve Car and Drone Vision | sUAS News
Metamaterials provide a way to get around many of the physical limitations that have previously defined how engineers could control radio, light, and sound waves. For example, while conventional lenses need their characteristic shape to bend light rays into focus, a metamaterial lens can bend light the same way while being perfectly flat. Metamaterials are made from repeating structures that are smaller than the wavelength of the electromagnetic radiation being manipulated. Echodyne makes its metamaterials by tracing out repeating patterns of copper wiring on an ordinary circuit board.+
Meta-material (MESA) vs Active (AESA)
A board with multiple layers of such wiring can direct radar beams. And applying different voltages to some parts of the wiring makes it possible to actively control the beam as a phase shifter would. “Any printed circuit board manufacturer could produce these,” says Driscoll.
Metamaterial Antenna Lens will allow a flat lens to act like a curved lens
AUTOMOTIVE RADAR USING A METAMATERIAL LENS - Patent application

Tianwei Deng; Peng Khiang Tan; Ruifeng Huang, "Polarization-independent tunable reflector," Antenna Technology and Applied Electromagnetics (ANTEM), 2014 16th International Symposium on , vol., no., pp.1,2, 13-16 July 2014
doi: 10.1109/ANTEM.2014.6887722
Abstract: In this paper, a novel tunable reflector with gain medium was designed, fabricated and measured. By incorporating active elements into two magnetic metamaterial SRRs, gain medium with positive loss, perfect losslessness and even negative loss can be tuned to switch the function of the active reflector among a perfect absorber, a perfect reflector and a gain reflector. The reflectivity of the tunable reflector can be tuned from -20dB to +15dB via three DC control channels. By introducing two more SRRs in one unit cell, polarization-independent function could be realized.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6887722&isnumber=6887652
Tripon-Canseliet, C.; Martinaud, J.-P.; Renard, C.; Chazelas, J., "Contribution of metamaterials to improvement of scan performance and reconfigurability of phased array antennas," Radar Conference (Radar), 2014 International , vol., no., pp.1,3, 13-17 Oct. 2014
doi: 10.1109/RADAR.2014.7060392
Abstract: This document presents insights on new generation multilayer `Tile' phased array antennas with inclusion of metamaterial structures interacting with electromagnetic wave propagation in order to improve radiating performance of the antenna (reduction/mitigation of `blindness' phenomenon, reduction of side and back radiation), and frequency agility by optical control.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7060392&isnumber=7060235

Mehrabani, A.M.; Shafai, L., "Planar, self-complementary, and wideband antennas with polarization diversity," Radio Science Meeting (Joint with AP-S Symposium), 2014 USNC-URSI , vol., no., pp.110,110, 6-11 July 2014
doi: 10.1109/USNC-URSI.2014.6955492
Abstract: Summary form only given. With the ever-growing technology progress in wireless communication systems, from cell phones, wireless computer tablets, and multimode Global Positioning Systems (GPS) to modern satellite and radar applications, the channel capacity enhancement is in increasing demand during the recent decades. One remedy, that has long been used, is to transmit and or receive signals over the same band of frequency, well known as frequency reuse systems. In these systems, two orthogonal waves are utilized for each transmit and or receive channel, thereby leading to a significant increase in the channel capacity. The orthogonality can be realized by two perpendicularly linearly polarized waves or two circularly polarized ones with opposite senses of polarization. In radar applications, the circular polarization not only improves the radar cross section response of the objects, but also helps better clutter suppression due to the raindrops. Therefore, antennas with the capability of generating both senses of circular polarization (CP) are of great importance in polarization diversity applications. The planar self-complementary antenna structures, such as spirals and helices, are the best candidates. As it is well known, the sense of polarization in a spiral antenna is determined by the direction of its winding. Therefore, a given spiral geometry presumably produces CP waves with a right- or left-handed sense. In the literature, an orthogonal mode helical antenna with dual senses of polarization was reported by (H.P. Coleman and B.D. Wright, IEEE Trans. Antennas Propag., 414-415, 1984), when it was fed from its both arm ends. This, however, results in a complex feeding network and increases the overall antenna weight and volume, when applied to N-arm spiral or helical antennas.In this paper, a planar, self-complementary, four-arm Archimedean spiral antenna is investigated. The proposed antenna is only center-fed and produces both righthanded and left-handed - P waves over the same frequency band of nearly 13GHz, with the spiral winding preset to the right direction. Based on the band theory, the dominant mode produces a CP axial beam, whose sense of polarization accords with the winding direction of the spiral. The opposite sense of polarization is then generated using higher order modes. The higher order modes, however, have boresight-null beams. Therefore, the proposed spiral antenna is carefully designed to always radiate broadside beams for both senses of polarization. Moreover, linear polarization, either vertical or horizontal, can be achieved by signal processing technique from the resultant CP waves with two senses of polarization. All the corresponding results of such a reconfigurable antenna with polarization diversity will be discussed and presented in the conference.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6955492&isnumber=6955372


Radar Components

Massa, A.; Oliveri, G., "Metasurface and metamaterial by design," Radar Conference (Radar), 2014 International , vol., no., pp.1,5, 13-17 Oct. 2014
doi: 10.1109/RADAR.2014.7060391
Abstract: The synthesis of high-performance and complex electromagnetic devices is carried out through an innovative approach. The features of metasurfaces and metamaterials are exploited to design innovative field manipulation devices. More in detail, a set of instances of the System-by-Design paradigm are applied to the synthesis of metasurface and metamaterial-enhanced electromagnetic devices in order to demonstrate the flexibility, modularity, and performance of the arising synthesis tools as well as of the obtained devices. Selected numerical examples are reported to give the readers some insights on the potentialities of the proposed synthesis framework.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7060391&isnumber=7060235
Apte, A.M.; Poddar, A.K.; Rudolph, M.; Rohde, U.L., "A Novel Low Phase Noise X-Band Oscillator," Microwave Magazine, IEEE , vol.16, no.1, pp.127,135, Feb. 2015
doi: 10.1109/MMM.2014.2367957
Abstract: In this article, we presented an X-band oscillator based on a novel CCMR using SIW technology. The measured results show that the proposed oscillator using active complementary coupled metamaterial has low phase noise and a good FOM for a given size and dc power consumption.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7010374&isnumber=7010136

Stealth

Metamaterial for Radar Frequencies - 12Sep_Tan_SzuHau.doc - a567346.pdf
Abstract - The objective of this thesis is to investigate a new design of periodic metamaterial (MTM) structure for radar cross-section (RCS) reduction application on aircraft and ships. MTMs are man-made materials, not found in nature, that exhibit unusual properties in the radio-, electromagnetic-, and optical-wave bands. The cells of these periodic MTM structures must be much smaller than the wavelength of the frequency of interest. In a MTM, the structure and dimensions of the design at the frequency of interest can produce negative values of permeability and/or permittivity, which define the electrical properties of the MTM. This study looks at various designs of absorbing layers presented in technical papers and verifies the results in simulations. Modifications are done to the existing designs to achieve good absorption level at the radar-frequency band of interest. Modeling and simulation are done in Microwave Studio by Computer Simulation Technology (CST). The S-parameters S11(reflection coefficient) and S12 (transmission coefficient) are used to investigate the performance of the MTM as a radar-frequency absorber.
EXPERIMENTAL VERIFICATION OF A TRIPLE BAND THIN RADAR ABSORBER METAMATERIAL FOR OBLIQUE INCIDENCE APPLICATIONS 07.13022207.pdf


Mahmoud A. Abdalla, Electromagnetic Fields Group, Electronic Engineering Department, MTC University, Cairo, Egypt

Abstract - This paper presents the theory, design, and experimental investigation of an ultra thin (6% wavelength) and triple band metamaterial radar absorber. The theoretical design of the reported absorber is investigated. The absorber performance was validated using the electromagnetic simulations and confirmed by experimental measurements for different incidence angles. The results confirm that the proposed metamaterial absorber can demonstrate triple bands with better than -15dB reflection coefficient for all incident angles.
Huang, C.; Pan, W.; Ma, X.; Luo, X., "Wideband Radar Cross Section Reduction of a Stacked Patch Array Antenna Using Metasurface," Antennas and Wireless Propagation Letters, IEEE , vol.PP, no.99, pp.1,1
doi: 10.1109/LAWP.2015.2407375
Abstract: In this paper, a two-layer metasurface is proposed to achieve radar cross section (RCS) reduction of a stacked patch antenna at a broad band. The lower layer metasurface is composed of four square patches loaded with four resistors, which is utilized to reduce RCS in the operation band (2.75 - 3.4 GHz) of the patch antenna. The periodic square loops with four resistors mounted on each side are adopted to construct the upper layer metasurface for absorbing the incoming wave out of band. We first investigate the effectiveness of the proposed metasurface on the RCS reduction of the single stacked patch and then apply this strategy to the 1×4 stacked patch array. The proposed low RCS stacked patch array antenna is fabricated and measured. The experimental results show that the designed metasurface makes the antenna RCS dramatically reduced in a broad band covering the operation band and out-of-band from 5.5-16 GHz. Moreover, the introduction of metasurface is demonstrated to have little influence on the antenna performance.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7050335&isnumber=4357943

Weiwei Xu; Junhong Wang; Meie Chen; Zhan Zhang; Zheng Li, "A Novel Microstrip Antenna With Composite Patch Structure for Reduction of In-Band RCS," Antennas and Wireless Propagation Letters, IEEE , vol.14, no., pp.139,142, 2015
doi: 10.1109/LAWP.2014.2357017
Abstract: A novel kind of composite patch antenna is proposed, in which the mushroom-like electromagnetic band-gap (EBG) structure is integrated onto the conventional patch. Due to the high impedance property of the EBG structure, the scattering fields from EBG structure and the rest of antenna can be out of phase and cancel each other. The composite patch antenna exhibits a natural low in-band radar cross section (RCS) property and keeps the compact planar size as the conventional patch antenna. When radiating, the composite patch as a whole acts as the radiating part of the antenna; while scattering, the composite patch antenna can significantly reduce the in-band RCS within the main scattering beam direction, and the maximum reduction can reach 8 dBsm when plane wave is impinging from normal direction.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6895248&isnumber=7024204

Balanis, C.; Chen, W.; Birtcher, C., "Checkerboard EBG Surfaces for Wideband Radar Cross Section Reduction," Antennas and Propagation, IEEE Transactions on , vol.PP, no.99, pp.1,1
doi: 10.1109/TAP.2015.2414440
Abstract: Abstract—Electromagnetic band-gap (EBG) structures have noteworthy electromagnetic characteristics that include their reflection phase variations with frequency. This paper applies this unique reflection phase property to alter the direction of the fields scattered by a radar target to reduce its Radar Cross Section (RCS). This redirecting of the scattered fields occurs when a surface is covered with a checkerboard of alternating EBG structures, and results in a wider frequency band RCS reduction. RCS reduction, compared to a PEC surface, of 10 dB can be realized over 60% frequency bandwidth. Simulations of monostatic and bistatic RCS of two dual EBG checkerboard surfaces, square and hexagonal, are compared with those of equal-sized PEC ground planes. The simulated monostatic RCS is also compared with measurements. Both TEz and TMz polarizations for oblique incidence are considered. Excellent agreement is obtained between simulated and measured patterns, for both the square and hexagonal EBG checkerboard surfaces. An approximate analytical expression is provided as a guideline for 10-dB RCS reduction of a dual EBG checkerboard surface compared to that of a PEC.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7063245&isnumber=4907023

Zhao, Y.; Yu, C.; Gao, J.; Yao, X.; Liu, T.; Li, W.; Li, S., "Broadband Metamaterial Surface for Antenna RCS Reduction and Gain Enhancement," Antennas and Propagation, IEEE Transactions on , vol.PP, no.99, pp.1,1
doi: 10.1109/TAP.2015.2415855
Abstract: This paper presents a broadband metamaterial surface with low radar cross section (RCS) and introduces its application on antenna. The metamaterial surface is composed of polarization-dependent artificial magnetic conductors (PDAMCs), which are orthogonal arranged in chessboard-like configuration for backscatter cancellation. By optimizing the PDAMC cell, effective phase difference is obtained in wideband and the surface achieves 10dB RCS reduction over the bandwidth of 32%. As a potential application, the metamaterial surface is employed to replace the metallic ground of a slot antenna. Illustrated by detecting wave, the novel antenna shows low RCS at boresight. While the antenna operates, the gain gets enhanced as a result of parasitic radiation of the surface. Full wave simulations and measurements validate that the novel antenna achieves both broadband low RCS and high gain compared with the slot antenna installed on a same-size metallic plate.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7065272&isnumber=4907023

Kiani, M.; Abdolali, A.; Salary, M.M., "EM Scattering From Cylindrical Structures Coated by Materials With Inhomogeneity in Both Radial and Azimuthal Directions," Antennas and Propagation, IEEE Transactions on , vol.63, no.3, pp.1118,1128, March 2015
doi: 10.1109/TAP.2015.2391289
Abstract: Consider a cylindrical structure with an arbitrary core coated by layers with inhomogeneity in both radial and azimuthal directions in the most general case. The core of the structure may be PEC, PMC, PEMC, impedance surface, dielectric, or metamaterial and an electromagnetic (EM) wave with arbitrary polarization is obliquely incident on the structure. In this paper, EM scattering from such a structure is analyzed, for the first time, through a general method in the frequency domain on the basis of the Taylor series concept. The validity of the proposed method is verified through some comprehensive examples. It is confirmed that the method is simple, fast, and highly reliable. Moreover, it is capable of analyzing the scattering of obliquely incident plane waves for all types of cylindrical cores and lossy inhomogeneous layers with continuous dielectric and magnetic profiles. In the last example, to show the applicability of the proposed method in inverse problems, the method is employed in an optimization procedure to reduce the radar cross section of a PEC cylinder.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7008459&isnumber=7052428
Ji-woong Jang; Haeseung Lee; Il-suek Koh; Ilsung Seo; Yongshik Lee, "Efficient calculation method of electromagnetic scattering by finite I-shaped metamaterial rectangular plate," Antennas and Propagation Society International Symposium (APSURSI), 2014 IEEE , vol., no., pp.2224,2225, 6-11 July 2014
doi: 10.1109/APS.2014.6905439
Abstract: The calculation method of the scattering by a finite metamaterial rectangular plate is proposed. The surface current distributions are modeled for a transverse electric(TE) and transverse magnetic(TM) waves. The proposed method is numerically and experimentally verified by comparing the Radar Cross Section(RCS).
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6905439&isnumber=6904322

Baskey, H.B.; Jha, A.K.; Akhtar, M.J., "Design of metamaterial based structure for the radar cross section reduction of a microstrip antenna," Microwave and RF Conference (IMaRC), 2014 IEEE International , vol., no., pp.104,107, 15-17 Dec. 2014
doi: 10.1109/IMaRC.2014.7038981
Abstract: In this paper, a novel metamaterial absorber working in the C band frequency range has been proposed to reduce the in-band Radar Cross Section (RCS) of a typical planar antenna. The absorber is first designed in the shape of a hexagonal ring structure having dipoles at the corresponding arms of the rings. The various geometrical parameters of the proposed metamaterial structure have first been optimized using the numerical simulator, and the structure is fabricated and tested. In the second step, the metamaterial absorber is loaded on a microstrip patch antenna working in the same frequency band as that of the metamaterial absorber to reduce the in-band Radar Cross Section (RCS) of the antenna. The prototype is simulated, fabricated and tested. The simulated results show the 99% absorption of the absorber at 6.35 GHz which is in accordance with the measured data. A close agreement between the simulated and the measured results shows that the proposed absorber can be used for the RCS reduction of the planar antenna in order to improve its in-band stealth performance.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7038981&isnumber=7038946
Massa, A.; Oliveri, G., "Metasurface and metamaterial by design," Radar Conference (Radar), 2014 International , vol., no., pp.1,5, 13-17 Oct. 2014
doi: 10.1109/RADAR.2014.7060391
Abstract: The synthesis of high-performance and complex electromagnetic devices is carried out through an innovative approach. The features of metasurfaces and metamaterials are exploited to design innovative field manipulation devices. More in detail, a set of instances of the System-by-Design paradigm are applied to the synthesis of metasurface and metamaterial-enhanced electromagnetic devices in order to demonstrate the flexibility, modularity, and performance of the arising synthesis tools as well as of the obtained devices. Selected numerical examples are reported to give the readers some insights on the potentialities of the proposed synthesis framework.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7060391&isnumber=7060235

Soheilifar, M.R.; Sadeghzadeh, R.A.; Aghakhani, M., "Design and fabrication of planar multi layer metamaterial absorber for RCS reduction," Antennas and Propagation (EuCAP), 2014 8th European Conference on , vol., no., pp.2039,2042, 6-11 April 2014
doi: 10.1109/EuCAP.2014.6902207
Abstract: In this paper, we report the design, simulation, and measurements of a new type of a broadband metamaterial absorber based on a periodic array of multi-layer structure resonators. The absorption band of our design is effectively extended by simply stacking several such structural layers with different geometrical dimensions.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6902207&isnumber=6901672

Sabah, C.; Dincer, F.; Karaaslan, M.; Unal, E., "Ultra-sensitive dual-band metamaterial absorber based on symmetric resonators," Microwaves, Radar, and Wireless Communication (MIKON), 2014 20th International Conference on , vol., no., pp.1,4, 16-18 June 2014
doi: 10.1109/MIKON.2014.6899921
Abstract: Ultra sensitive metamaterial-based absorber (MA) which acts as a strong dual-band resonator is designed and constructed. The proposed model is based on symmetric ring resonator with gaps and octa-star strip (OSS) which allows maximization in the absorption at the resonances. Two maxima in the absorption are experimentally and numerically obtained with good agreement. The numerical studies verify that the dual-band MA can provide perfect absorption at wide angles of polarization and incidence waves. The proposed model can easily be used in many potential application areas such as security systems, sensors, medical imaging technology, and so on.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6899921&isnumber=6899823
Wengang Chen; Balanis, C.A., "Bandwidth enhancement for RCS reduction using checkerboard EBG surfaces," Antenna Technology and Applied Electromagnetics (ANTEM), 2014 16th International Symposium on , vol., no., pp.1,2, 13-16 July 2014
doi: 10.1109/ANTEM.2014.6887720
Abstract: The properties of Electromagnetic Band-Gap (EBG) structures are used to alter the scattering fields by combining Perfect Electric Conductor (PEC) and EBG structures on the same ground plane. Due to the anti-phase property, the reflected energy can be re-directed toward four quadrants and a null to appear toward the normal direction. To increase the bandwidth, checkerboard surfaces of different EBG structures on the same ground plane are proposed. Two different configurations of EBG structures are designed to realize the 180° phase difference, in order to achieve a wider band Radar Cross Section (RCS) reduction. The RCS of the surfaces are compared with those of the equal-sized PEC ground planes.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6887720&isnumber=6887652

Bhattacharyya, Somak; Ghosh, Saptarshi; Srivastava, Kumar Vaibhav, "Equivalent circuit modeling of an ultra-thin dual-band microwave metamaterial absorber," Microwave Conference (APMC), 2014 Asia-Pacific , vol., no., pp.1244,1246, 4-7 Nov. 2014
Abstract: This paper presents the equivalent circuit modeling of an ultra-thin microwave metamaterial absorber comprising two concentric closed ring resonator (CRR) structures. The dimension of the unit cell as well as the other geometrical parameters like radii and widths of the rings are optimized so that absorptions take place at two distinct frequencies near to the middle of the FCC radar frequency spectrum. The proposed structure shows peak absorptivities of 93.4% and 99.6% at 5.50 GHz and 9.52 GHz respectively. The equivalent circuit of each CRR is proposed and the overall circuit model is developed accordingly. The simulation of the proposed equivalent circuit agrees well with the numerical simulation, thus validating the modeling. The structure is also fabricated whose results match closely.
keywords: {Abstracts;Decision support systems;Microstrip filters;Microwave filters;Optical filters;Physics;Absorber;Closed Ring Resonator (CRR) Structure;Dual-Band;Equivalent Circuit Modeling;Metamaterials},
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7067625&isnumber=7067568

Smythe, B.; Casserly, S.; Arakaki, D., "Organic-based microwave frequency absorbers using corn stover," Antennas and Propagation Society International Symposium (APSURSI), 2014 IEEE , vol., no., pp.920,921, 6-11 July 2014
doi: 10.1109/APS.2014.6904788
Abstract: Commercial antenna test chambers (anechoic) currently use polyurethane foam absorbers on chamber interiors to eliminate undesired radio-frequency (RF) reflections. While effectively absorbing microwave signals, polyurethane material particulates over time adding contaminants to clean rooms and reducing absorber lifetime. These absorbers also release toxic gas when operating under high temperatures and pose a health risk to direct-contact personnel. This paper presents reflectivity analysis and performance of alternative organic-based (corn stover) microwave frequency absorbers for use in anechoic chambers. These absorbers are composed of renewable materials and eliminate the toxic gas release problem for polyurethane materials under high power test conditions. Preliminary results show that the organic absorbers perform at levels comparable to commercially-available absorber panels.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6904788&isnumber=6904322

Chaurasiya, D.; Ghosh, S.; Srivastava, K.V., "Dual band polarization-insensitive wide angle metamaterial absorber for radar application," European Microwave Conference (EuMC), 2014 44th , vol., no., pp.885,888, 6-9 Oct. 2014
doi: 10.1109/EuMC.2014.6986577
Abstract: In this paper, an ultra-thin dual-band polarization-insensitive metamaterial absorber with wide-angle characteristics has been presented. The unit cell geometry comprises two circular rings with the inner one cross-connected. Simulated results show two discrete absorption peaks at 2.90 GHz (S-band) and 6.13 GHz (C-band) with absorptivities of 99.66% and 99.83% respectively, which can be used for surveillance and air defense radar applications. The proposed structure is polarization-insensitive and shows high absorption (over 80%) for wide incident angles upto 60 degree for both TE and TM polarizations. The proposed structure has been fabricated and measured, showing good agreement with the simulated responses.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6986577&isnumber=6986339



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