scholarly journals An Ultrawideband Polarization-Insensitive Diffusion Metasurface Using Period Changed Unit Cell for RCS Reduction

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5053
Author(s):  
Jianzhong Chen ◽  
Chengwei Zhang ◽  
Yutong Zhao ◽  
Lei Lin ◽  
Liang Li ◽  
...  
Keyword(s):  
Cross Section ◽  
Phase Difference ◽  
Rotational Symmetry ◽  
Radar Cross Section ◽  
Unit Cell ◽  
Operating Frequency ◽  
Reflection Amplitude ◽  
Good Consistency ◽  
Unit Cells ◽  
Polarization Insensitive

A polarization-insensitive diffusion metasurface using a period-changed unit cell is presented for reducing the radar cross-section (RCS) of metallic objects in ultrawideband. Two metallic Minkowski loops are proposed as coding elements, different from traditional designs. The “0” element is constructed by period-changed unit cells to achieve a 180 ± 30° phase difference with the same reflection amplitude of nearly −0.9 dB in an ultrawideband from 7.1 to 29.2 GHz. Multilayer geometry with a thickness of 4.5 mm (about 0.105λ0 at the lowest operating frequency) and rotational symmetry loops are used to realize the ultrawideband characteristic and polarization-insensitive behavior. For verification, a polarization-insensitive diffusion metasurface is designed, fabricated, and measured. The simulated and measured results of the diffusion metasurface are in good consistency and the results both show that the metasurface enables a 10 dB backscattering reduction over an amazing ultrawideband ranging from 7.1 to 29.2 GHz (BW of 122%).

Radar cross-section reduction based on an iterative fast Fourier transform optimized metasurface

2016 ◽  
Vol 30 (18) ◽  
pp. 1650233 ◽  
Author(s):  
Yi-Chuan Song ◽  
Jun Ding ◽  
Chen-Jiang Guo ◽  
Yu-Hui Ren ◽  
Jia-Kai Zhang
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Cross Section ◽  
Radar Cross Section ◽  
Simulation Software ◽  
Pattern Synthesis ◽  
Array Pattern ◽  
Unit Cells ◽  
Polarization Insensitive ◽  
Geometry Parameter

A novel polarization insensitive metasurface with over 25 dB monostatic radar cross-section (RCS) reduction is introduced. The proposed metasurface is comprised of carefully arranged unit cells with spatially varied dimension, which enables approximate uniform diffusion of incoming electromagnetic (EM) energy and reduces the threat from bistatic radar system. An iterative fast Fourier transform (FFT) method for conventional antenna array pattern synthesis is innovatively applied to find the best unit cell geometry parameter arrangement. Finally, a metasurface sample is fabricated and tested to validate RCS reduction behavior predicted by full wave simulation software Ansys HFSS[Formula: see text] and marvelous agreement is observed.

scholarly journals Wideband RCS Reduction Using Coding Diffusion Metasurface

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2708 ◽  
Author(s):  
Ali ◽  
Li ◽  
Khan ◽  
Yi ◽  
Chen
Keyword(s):  
Cross Section ◽  
Phase Difference ◽  
Frequency Band ◽  
Optimization Algorithm ◽  
Radar Cross Section ◽  
Reduction Technique ◽  
Metallic Plate ◽  
Random Optimization ◽  
Unit Cells ◽  
Working Frequency

This paper presents a radar cross-section (RCS) reduction technique by using the coding diffusion metasurface, which is optimised through a random optimization algorithm. The design consists of two unit cells, which are elements ‘1’ and ‘0’. The reflection phase between the two-unit cells has a 180° ± 37° phase difference. It has a working frequency band from 8.6 GHz to 22.5 GHz, with more than 9 dB RCS reduction. The monostatic RCS reduction has a wider bandwidth of coding diffusion metasurface as compared to the traditional chessboard metasurface. In addition, the bistatic performance of the designed metasurfaces is observed at 15.4 GHz, which shows obvious RCS reduction when compared to a metallic plate of the same size. The simulated and measured result shows the proficiency of the designed metasurface.

scholarly journals An efficient method for indexing grazing-incidence X-ray diffraction data of epitaxially grown thin films

2020 ◽  
Vol 76 (3) ◽  
pp. 345-357 ◽  
Author(s):  
Josef Simbrunner ◽  
Benedikt Schrode ◽  
Jari Domke ◽  
Torsten Fritz ◽  
Ingo Salzmann ◽  
...  
Keyword(s):  
Rotational Symmetry ◽  
Grazing Incidence ◽  
Unit Cell ◽  
Structure Identification ◽  
X Ray Diffraction ◽  
Cell Parameters ◽  
Lattice Constants ◽  
The Matrix ◽  
Unit Cells ◽  
Complex Scenario

Crystal structure identification of thin organic films entails a number of technical and methodological challenges. In particular, if molecular crystals are epitaxially grown on single-crystalline substrates a complex scenario of multiple preferred orientations of the adsorbate, several symmetry-related in-plane alignments and the occurrence of unknown polymorphs is frequently observed. In theory, the parameters of the reduced unit cell and its orientation can simply be obtained from the matrix of three linearly independent reciprocal-space vectors. However, if the sample exhibits unit cells in various orientations and/or with different lattice parameters, it is necessary to assign all experimentally obtained reflections to their associated individual origin. In the present work, an effective algorithm is described to accomplish this task in order to determine the unit-cell parameters of complex systems comprising different orientations and polymorphs. This method is applied to a polycrystalline thin film of the conjugated organic material 6,13-pentacenequinone (PQ) epitaxially grown on an Ag(111) surface. All reciprocal vectors can be allocated to unit cells of the same lattice constants but grown in various orientations [sixfold rotational symmetry for the contact planes (102) and (102)]. The as-determined unit cell is identical to that reported in a previous study determined for a fibre-textured PQ film. Preliminary results further indicate that the algorithm is especially effective in analysing epitaxially grown crystallites not only for various orientations, but also if different polymorphs are present in the film.

scholarly journals Plasmon resonances management of meta-mirror for combining radar cross section (RCS) reduction and specular reflection with frequency selectivity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Pesarakloo ◽  
Alireza Oruji
Keyword(s):  
Cross Section ◽  
Incident Wave ◽  
Specular Reflection ◽  
Radar Cross Section ◽  
Unit Cell ◽  
Frequency Selectivity ◽  
Polarization Conversion ◽  
Plasmon Resonances ◽  
Specific Frequency

AbstractIn this paper using Plasmon Resonances Management (PRM), a bi-functional meta-mirror is proposed in which, the meta-mirror can obtain two opposite properties in two different frequency ranges. In this method, an anisotropic unit cell with polarization conversion property is modified to have two plasmon resonances in both symmetric and anti-symmetric planes in a specific frequency. This allows the unit cell to have the property of unchanged polarization in that frequency. The meta-mirror is composed of this modified unit cell and its mirror as a chessboard arrangement and the incident wave on the meta-mirror is reflected as in-phase in that specific frequency i.e. specular reflection, while as out-of-phase in other frequencies i.e. RCS reduction. The designed meta-mirror in this paper demonstrates the RCS reduction in two side-bands from 4 to 9 GHz and 10.8 to 14.8 GHz while behaving as a specular reflection in the frequency around 10 GHz.

scholarly journals Gain-Enhanced Metamaterial Absorber-Loaded Monopole Antenna for Reduced Radar Cross-Section and Back Radiation

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1247
Author(s):  
Heijun Jeong ◽  
Yeonju Kim ◽  
Manos M. Tentzeris ◽  
Sungjoon Lim
Keyword(s):  
Cross Section ◽  
Radar Cross Section ◽  
Metamaterial Absorber ◽  
Monopole Antenna ◽  
Magnetic Conductor ◽  
Low Profile ◽  
Before And After ◽  
Unit Cells ◽  
Lumped Elements ◽  
Peak Gain

This paper proposes a gain-enhanced metamaterial (MM) absorber-loaded monopole antenna that reduces both radar cross-section and back radiation. To demonstrate the proposed idea, we designed a wire monopole antenna and an MM absorber. The MM absorber comprised lumped elements of subwavelength unit cells and achieved 90% absorbance bandwidth from 2.42–2.65 GHz. For low-profile configurations, the MM absorber was loaded parallel to and 10 mm from the monopole antenna, corresponding to 0.09 λ0 at 2.7 GHz. The monopole antenna resonated at 2.7 GHz with a 3.71 dBi peak gain and 2.65 GHz and 6.46 dBi peak gain, before and after loading the MM absorber, respectively. Therefore, including the MM absorber increased peak gain by 2.7 dB and reduced back radiation by 15 dB. The proposed antenna radar cross-section was reduced by 2 dB compared with a monopole antenna with an artificial magnetic conductor.

Correlation of Thermal Conductivities of Unidirectional Fibrous Composites Using Local Fractal Techniques

1991 ◽  
Vol 113 (4) ◽  
pp. 788-796 ◽  
Author(s):  
R. Pitchumani ◽  
S. C. Yao
Keyword(s):  
Cross Section ◽  
Volume Fraction ◽  
Fibrous Composite ◽  
Flow Direction ◽  
Fractal Dimensions ◽  
Unit Cell ◽  
Small Range ◽  
Fiber Volume ◽  
Unit Cells ◽  
Traditional Approaches

The arrangement of fibers strongly influences heat conduction in a composite. Traditional approaches using unit cells to describe the fiber arrangements work well in the case of ordered arrays, but are not useful in the context of disordered arrays, which have been analyzed in the literature by statistical means. This work presents a unified treatment using the tool of local fractal dimensions (although, strictly speaking, a composite cross section may not be an exact fractal) to reduce the geometric complexity of the relative fiber arrangement in the composite. The local fractal dimensions of a fibrous composite cross section are the fractal dimensions that it exhibits over a certain small range of length scales. A generalized unit cell is constructed based on the fiber volume fraction and local fractal dimensions along directions parallel and transverse to the heat flow direction. The thermal model resulting from a simplified analysis of this unit cell is shown to be very effective in predicting the conductivities of composites with both ordered as well as disordered arrangement of fibers. For the case of square packing arrays, the theoretical result of the present analysis is identical to that of Springer and Tsai (1967).

scholarly journals Radar Cross Section Reduction Techniques using Metamaterials

2019 ◽  
Vol 8 (9S) ◽  
pp. 103-111
Keyword(s):  
Cross Section ◽  
Radar Cross Section ◽  
Unit Cell ◽  
Military Technology ◽  
Antenna Performance ◽  
Reduction Techniques ◽  
Stealth Technology ◽  
Research Activities ◽  
Electromagnetic Responses ◽  
Increasing Demand

In this paper, we have discussed and summarized the techniques of radar cross section reduction (RCSR). RCSR has been prompted due to the evolution of military technology. The paper reviews the basic concepts and characteristics of metamaterials, as these are the most favorable development that impacts defense industry products and stealth technology. This paper emphasizes the role of airpower and the ever-increasing demand for stealth. Initially, the blending of the fundamental aspects of stealth technology through radar signatures and methods of signature reduction are discussed. Then, the description of metamaterials and detailed analysis of their properties is made. This paper review the fundamental properties of metamaterials. It also explores the recent research activities on metamaterials in various areas. Some existing researches techniques used for RCSR are examined. The metamaterials are engineered media whose electromagnetic responses are different from those of their constituent components. The general benefits of metamaterials are pointed out in the paper. Metamaterials are mostly used in antenna configuration for enhancing antenna performance such as realizing miniaturization, expanding the operating band, enhancing gain as well as reducing RCS. These characteristics of the metamaterials are basically the reason why metamaterials should be used in stealth technology. The various categories of metamaterials used for RCSR are studied in the paper. In this paper, we have also proposed a unit cell. The unit cell consists of a square loop and intersecting strips at the edges of add shaped structure.

scholarly journals Minimization of Mutual Coupling in Arrays using Cross-shape EBG

2019 ◽  
Vol 8 (11) ◽  
pp. 2599-2603
Keyword(s):  
Band Gap ◽  
Mutual Coupling ◽  
Unit Cell ◽  
Operating Frequency ◽  
Design Parameters ◽  
Substrate Thickness ◽  
Electromagnetic Band Gap ◽  
Area Reduction ◽  
Unit Cells ◽  
Current Scenario

In current scenario, the utilization of Electromagnetic Band Gap (EBG) has increased tremendously in microwave engineering. Mutual Coupling (MC) is a significant constraint to be measured in antennas specialization when used with arrays. Electromagnetic Band-Gap (EBG) is a well-known procedure applied in microwave and RF region due to its inherent bandgap feature at predefined frequency. MC arises due to surface currents excited on printed arrays whenever the substrate thickness ℇr > 1. By incorporating EBG in between array elements, various parameters like bandwidth, gain, radiation pattern, directivity, and current distribution can be improved based on the design parameters. Compactness and patch area reduction can be achieved through suitable unit cells of EBG structures. A patch performance is effective with better radiation characteristics and good return loss provided the operating frequency fall within the operating frequency of the unit-cell of the EBG. The unit cell can be constructed depending on the reflection phase, dispersion diagram. In this, a cross-EBG is used to enhance the MC between the arrays. The Cross EBG size is 6.3mm x 6.3mm. The antenna resonates at 5.8GHz WLAN range.

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