Towards active dispersionless ENZ metamaterial for cloaking applications

Hrabar, Silvio; Krois, Igor; Kiricenko, Aleksandar

doi:10.1016/j.metmat.2010.07.001

Cited by 66 publications

(71 citation statements)

References 15 publications

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“…Both aspects have to be treated with extreme caution. Recent experiments on metamaterials composed of active non-Foster elements operating at MHz and GHz frequencies [20,21] have shown rather constant superluminal electromagnetic phase and group velocities from 2 MHz to 40 MHz frequency [21] (more than four octaves bandwidth). The frequency dependence occurring at yet higher frequencies guarantees the fundamental consistency with causality and with the laws of special relativity [20,21].…”

Section: Resultsmentioning

confidence: 99%

Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics

Halimeh¹,

Wegener²

2012

Opt. Express

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Abstract:The design rules of transformation optics generally lead to spatially inhomogeneous and anisotropic impedance-matched magnetodielectric material distributions for, e.g., free-space invisibility cloaks. Recently, simplified anisotropic non-magnetic free-space cloaks made of a locally uniaxial dielectric material (calcite) have been realized experimentally. In a two-dimensional setting and for in-plane polarized light propagating in this plane, the cloaking performance can still be perfect for light rays. However, for general views in three dimensions, various imperfections are expected. In this paper, we study two different purely dielectric uniaxial cylindrical free-space cloaks. For one, the optic axis is along the radial direction, for the other one it is along the azimuthal direction. The azimuthal uniaxial cloak has not been suggested previously to the best of our knowledge. We visualize the cloaking performance of both by calculating photorealistic images rendered by ray tracing. Following and complementing our previous ray-tracing work, we use an equation of motion directly derived from Fermat's principle. The rendered images generally exhibit significant imperfections. This includes the obvious fact that cloaking does not work at all for horizontal or for ordinary linear polarization of light. Moreover, more subtle effects occur such as viewing-angle-dependent aberrations. However, we still find amazingly good cloaking performance for the purely dielectric azimuthal uniaxial cloak.

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Section: Resultsmentioning

confidence: 99%

Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics

Halimeh¹,

Wegener²

2012

Opt. Express

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“…The prototype presented here works up to 200 MHz due to the fact that as a rule of thumb NICs only work up to a frequency ten times smaller than the transient frequency of the transistors [30]. The transistor employed here (BF998) has a transient frequency of 1.9 GHz, so the prototype presents the expected bandwidth.…”

Section: Design Examplementioning

confidence: 99%

Stability Analysis and Design of Negative Impedance Converters: Application to Circuit and Small Antennas

Ugarte-Munoz¹,

Jiménez-Martín²,

Segovia-Vargas³

et al. 2016

RADIOENGINEERING

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“…From the circuit theory point of view, one may say that the dispersion in passive metamaterials occurs due to the basic difference in the frequency behavior of a capacitor and an inductor. Very recently, it has been shown that, in some cases, it is possible to overcome basic dispersion constrains (1,2) by the use of electronic circuits that behave as negative capacitors or negative inductors (so-called non-Foster elements [5][6][7][8][9]). The simplest implementation (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Since the dispersion curves of a positive capacitor and a negative capacitor are exactly inverse, the resultant behavior (4) does not depend on the frequency at all. This novel principle was successfully employed in several practical realizations of active ENZ metamaterials [6][7][8] and achieved bandwidths varied from one octave [6,7] to more than four octaves [8]. These bandwidths are significantly better than the bandwidth of all passive metamaterials available at present.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the fact that the equivalent relative permittivity is smaller than one within an extremely broad band enables the propagation with phase and group velocities higher than speed of light (superluminal propagation [8]). Numerical simulations (based on actual measurement results) in [7] clearly showed that non-Foster active ENZ metamaterial may enable construction of broadband cloaking devices. Several other applications such as dispersionless feeding networks in antenna arrays and broadband phase shifters in communication technology were also foreseen [8].…”

Section: Introductionmentioning

confidence: 99%

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Stability Analysis of Superluminal Metamaterial Transmission Line with Realistic Non-Foster Negative Capacitors

2012

Self Cite

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Original scientific paperRecently, it has been shown possible to go around basic dispersion energy constraints that limit bandwidth of every passive metamaterial and construct a broadband active Epsilon-Near-Zero superluminal transmission line. A basic building block of this unusual transmission line is an active 'tank circuit' that contains both conventional (positive) capacitor and non-Foster negative capacitor. Published theoretical studies revealed that such a 'tank circuit' is stable if an overall capacitance is positive. These studies assumed lossless host transmission line periodically loaded with ideal dispersionless negative capacitors. However, a possible influence of the imperfections of a realistic negative capacitor (its dispersion and loss/gain) on the stability has not been investigated so far. Here, stability analysis of realistic superluminal transmission line is performed in Laplace domain. The obtained results are in a good agreement with those obtained in recent experiments on active transmission line developed at University of Zagreb.Key words: Non-Foster Element, Negative Capacitor, Stability, Metamaterial, Superluminal Propagation Analiza stabilnosti superluminalne prijenosne linije temeljene na metamaterijalu s neidalnim neFosterovim negativnim kondenzatorima. Nedavno je pokazano da je moguće zaobići temeljne energetskodisperzijske uvjete koji ograničavaju širinu frekvencijskog pojasa svakog pasivnog metamaterijala. Takoîer je pokazano da je moguće konstruirati širokopojasnu aktivnu superluminalnu prijenosnu liniju s približno nultom permitivnosti (ENZ). Osnovni gradivni element ove neuobičajne linije je aktivni "titrajni krug" koji se sastoji od klasičnog (pozitivnog) i ne-Fosterovog negativnog kondenzatora. Do sada objavljene teorijske studije pokazale su da je ovakav "titrajni krug" stabilan ako je ekvivalentni ukupni kapacitet pozitivan. Meîutim, stvarni (neidalni) negativni kondenzator uvijek ima gubitke (ili pojačanje) i disperziju. Utjecaj ovih nesavršenosti na stabilnost superluminalne linije je nejasan i do sada nije istraživan. Stoga je u ovomečlanku načinjena analiza stabilnosti neidealne superluminalne prijenosne u Laplaceovoj domeni. Rezultati analize su u vrlo dobrom suglasju s nedavno objavljenim rezultatima mjerenja na aktivnoj superluminalnoj prijenosnoj liniji koja je razvijena na Sveučilištu u Zagrebu.

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Towards active dispersionless ENZ metamaterial for cloaking applications

Cited by 66 publications

References 15 publications

Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics

Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics

Stability Analysis and Design of Negative Impedance Converters: Application to Circuit and Small Antennas

Stability Analysis of Superluminal Metamaterial Transmission Line with Realistic Non-Foster Negative Capacitors

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