Dual-band, double-negative, polarization-independent metamaterial for the visible spectrum

We present the first dual-band negative index metamaterial that operates in the visible spectrum. The optimized four-functional-layer metamaterial structure exhibits the first double-negative (i.e., simultaneously negative permittivity and permeability) band in the red region of the visible spectrum with a figure of merit of 1.7 and the second double-negative band in the green region of the visible spectrum with a figure of merit of 3.2. The optical behavior of the proposed structure is independent of the polarization of the incident field. This low-loss metamaterial structure can be treated as a modified version of a fishnet metamaterial structure with an additional metal layer of different thickness in a single functional layer. The additional metal layer extends the diluted plasma frequency deep into the visible spectrum above the second order magnetic resonance of the structure, hence provides a dual band operation with simultaneously negative effective permittivity and permeability. Broadband metamaterials with multiple negative index bands may be possible with the same technique by employing higher order magnetic resonances. The structure can be fabricated with standard microfabrication techniques that have been used to fabricate fishnet metamaterial structures.Comment: 26 Pages, 6 Figures, 2 Tables, 2 Medi

Tomorrow's Metamaterials: Manipulation of Electromagnetic Waves in Space, Time and Spacetime

Metamaterials represent one of the most vibrant fields of modern science and technology. They are generally dispersive structures in the direct and reciprocal space and time domains. Upon this consideration, I overview here a number of metamaterial innovations developed by colleagues and myself in the holistic framework of space and time dispersion engineering. Moreover, I provide some thoughts regarding the future perspectives of the area

Size reduction of microstrip antennas using left-handed materials realized by complementary split-ring resonators

Recently, metamaterials (MTMs) engineered to have negative values of permittivity and permeability, resulting in a left-handed system, have provided a new frontier for microwave circuits and antennas with possibilities to overcome limitations of the right-handed system. Microwave circuit components such as waveguides, couplers, power dividers and filters, constructed on left-handed materials, have demonstrated properties of backward coupling, phase compensation, reduced sizes, and propagation of evanescent modes. However, there is very limited work to date, on the microstrip antennas with metamaterials. Microstrip antenna is widely used for its low-profile, simplicity of feed and compatibility with planar microstrip circuitry. As the trend towards miniaturization of electronic circuitry continues, antennas remain as the bulkiest part of wireless devices. There are three primary objectives to the present work: 1. Explore the possibility of miniaturizing microstrip patch antennas using left-handed materials through phase-compensation 2. Achieve negative permittivity using Complementary Split-Ring Resonators (CSRR) 3. Implement CSRR in the ground plane of a rectangular patch antenna, and validate through simulation and measurement A rectangular patch antenna with a combined DPS-DNG substrate has been analyzed with the cavity model, from which the condition for mode propagation has been derived. Criteria for ‘electrically small’ patch, using phase-compensation have been developed and propagating modes that satisfy these criteria have been obtained. With an objective to design practically realizable antennas, amongst several available LHM structures, the Complementary Split Ring Resonators (CSRR) has been chosen, primarily for the ease of implementation in the ground plane. CSRRs are periodic structures which alter the bulk effective permittivity of a host medium in which they are embedded. The effective permittivity becomes negative in a certain frequency band defined as a ‘stop-band’. In the present work the frequency response of the CSRR and the ‘stop-band’ has been determined using a full wave solver, from which, effective permittivity of the composite with CSRRs has been obtained by parameter extraction. Finally, several combinations of patch and CSRR in the ground plane have been designed and constructed in the X-band frequency range. Measurements of input characteristics and directivity have been validated through simulation by Ansoft Designer and HFSS. It has been observed that the best designs are achieved when the ‘stop-band’ of the CSRR corresponds to the desired resonant frequency of the antenna. Under these conditions, a size reduction of up to fifty percent has been achieved and it is noted that the back lobe is negligible and the directivity is comparable to that of a right-handed microstrip antenna

Design of Left-handed Material Units and Their Antennas Based on Irregular/Asymmetric Structures

左手材料表现出很多奇特的电磁特性，使其在电磁学、微波和天线工程以及材料学等诸多领域拥有广阔的应用前景。目前，工作于微波频段的左手材料单元结构变化有很大一部分来源于经典的开口谐振环加金属线结构(SRR+Rod)，主要以规则、对称构型，一般双负频带窄、损耗大、尺寸也偏大，难以应用于有特殊性能要求和空间限制的微波器件。 本文针对目前微波频段左手材料所存在的以上缺点，提出了不规则及非对称两个系列的左手材料单元结构，即DNA形仿生结构和R形结构。在DNA形仿生系列中，首先讨论了双螺旋左手结构单元，该结构以较小的尺寸在10GHz左右形成了较宽的双负特性频带，并且损耗很低。接着在此双螺旋左手结构中引入交指...Left handed materials show a lot of unusual electromagnetic characteristics, which makes them have broad application prospects in many fields, such as electromagnetism, microwave and antenna engineering, material science and so on. At present, most structural deformations of left-handed material units working in microwave frequency bands derived from the classical open resonant ring and metal wir...学位：工程硕士院系专业：信息科学与技术学院_工程硕士(电子与通信工程)学号：2312013115312

A Miniaturized Printed Circuit CRLH Antenna-based Hilbert Metamaterial Array

With the development of communication systems and antennas, various challenges arise that require antennas of small size with enhanced performance. Metamaterials (MTM) defects introduced a considerable solution to such a challenge. Therefore, in this paper, a lightweight with low profile antenna is designed based on a novel design of a Composite Right/Left-Handed CRLH-MTM Hilbert array. The proposed CRLH-MTM unit cell consists of a T-symmetric CRLH unit cell conjugated to the 3rd-order Hilbert on the ground plane through a T-stub structure to enhance the gain-bandwidth product. CST-MWS is used to stimulate and design the proposed antenna structure. The antenna parameters are optimized to evaluate the antenna performance in gain and S11. As a result, the antenna can operate forward and backwards with a large scanning angle ranging from +34o to -134o with changing frequency, and dual-band extended from 3.3GHz to 4.2GHz 4.86GHz 5.98GHz with a maximum gain of 7.24dBi and 3.74dBi, respectively. The beam steering is achieved by trough controlling the switching operation of PIN diodes. As a result, the antenna can scan up to 8° from 34° to 42° at 3.5GHz with constant gain along with the operating range

'Growing Evanescent Envelopes and Anomalous Tunneling' in Cascaded Sets of Frequency-Selective Surfaces in Their Stop Bands

The presence of wave tunneling and the 'growing evanescent envelope' for field distributions in suitably designed, periodically layered stacks of frequency selective surfaces (FSS) is discussed in this paper. Here it is shown that a setup completely different completely different from the Pendry's lens allows an analogous buildup of evanescently modulated waves. In particular, it is shown how an interface resonance phenomenon similar to the one present at the interface between metamaterials with oppositely signed constitutive parameters may be induced by a proper choice of the periodicities of the FSS stacks and the geometrical properties of these surfaces. The analysis is performed through an equivalent transmission-line approach, and some physical insights into this phenomenon are presented. Salient features, such as the complete wave tunneling through the pair of cascaded FSS, each operating at its bandgap, are presented and discussed.Comment: 5 pages, 2 figures, submitted to Physical review

State-of-the-Art of Metamaterials: Characterization, Realization and Applications

Metamaterials is a large family of microwave structures that produces interesting ε and μ conditions with huge implications for numerous electromagnetic applications. Following a description of modern techniques to realize epsilon-negative, mu-negative and double-negative metamaterials, this paper explores recent literature on the use of metamaterials in hot research areas such as metamaterial-inspired microwave components, antenna applications and imaging. This contribution is meant to provide an updated overview of complex microwave engineering for the generation of different types of metamaterials and their application in topical electromagnetic scenarios

Impedance Transformers

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