Loss compensation in Metamaterials through embedding of active transistor based negative differential resistance circuits

Xu, Wangren; Padilla, Willie J.; Sonkusale, Sameer

doi:10.1364/oe.20.022406

Cited by 24 publications

(18 citation statements)

References 41 publications

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“…This NDR can be equivalently considered as a negative resistance À R d , acting as a current source linearly controlled by an applied voltage. Similar NDR device was used to improve the quality factor of a split ring resonator (SRR) by partially compensating its loss 11 . In Fig.…”

Section: Resultsmentioning

confidence: 99%

“…However, the inevitable loss due to their strongly dispersive nature is one of the fundamental challenges preventing such applications from becoming a reality. Recently, the discussions of incorporating active elements into artificial media to compensate loss and potential bandwidth have attracted more and more interests [3][4][5][6][7][8][9][10][11][12][13] . However, intense controversies on the causality issue of artificial active media still exist.…”

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confidence: 99%

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Microwave gain medium with negative refractive index

Chang

Ran

et al. 2014

Nat Commun

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Artificial effective media are attractive because of the fantastic applications they may enable, such as super lensing and electromagnetic invisibility. However, the inevitable loss due to their strongly dispersive nature is one of the fundamental challenges preventing such applications from becoming a reality. In this study, we demonstrate an effective gain medium based on negative resistance, to overcompensate the loss of a conventional passive metamaterial, meanwhile keeping its original negative-index property. Energy conservation-based theory, full-wave simulation and experimental measurement show that a fabricated sample consisting of conventional sub-wavelength building blocks with embedded microwave tunnel diodes exhibits a band-limited Lorentzian dispersion simultaneously with a negative refractive index and a net gain. Our work provides experimental evidence to the assertion that a stable net gain in negative-index gain medium is achievable, proposing a potential solution for the critical challenge current metamateiral technology faces in practical applications.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Microwave gain medium with negative refractive index

Chang

Ran

et al. 2014

Nat Commun

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“…A common method to improve the meta-atoms is to use active circuits [15,[19][20][21], for example, by using negative impedance converters. However, active circuits may have serious problems such as stability [19,25] and the requirement of an external power source.…”

Section: Improved Meta-atom With Active Circuitsmentioning

confidence: 99%

“…There have been attempts to overcome these problems by using active elements. When the frequency is low enough, large wavelengths allow one to use lumped elements such as inductors and capacitors but also electronic parts in a meta-atom [15][16][17][18][19][20][21]. In this paper, we first discuss the basic principles of a magnetic metaatom and the concepts to improve its response.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field Shielding by Metamaterials

Boyvat¹,

Hafner²

2013

PIER

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Abstract-Magnetic field shielding at low frequencies is a problem of high importance that is known for a long time. Metamaterials, which are known from fancy applications such as the so-called perfect lens and cloaking, also offer a new way to create efficient magnetic shielding by means of anisotropic metamaterials with low permeability in one direction. Such metamaterials can be constructed by assembling arrays of relatively simple LC circuits. In this paper, we analyze different metamaterials and show how they may be designed. We show that typical resistive losses in the coils and capacitors of the LC circuits reduce the shielding quality. Then, we consider the possibility of active electronic loss compensation and discuss the drawbacks of this concept. After this, we propose a purely passive way that benefits from the inhomogeneity of the magnetic field to be shielded. Finally, we present experimental results, which show the performance of metamaterial shields.

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“…At the circuit level, transistors are used for amplication, oscillation generation, and switching, providing several crucial active functions in electronic circuits. However, transistors have only recently been embedded in metamaterials through simple circuits and applications [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Bandwidth Tuning in Transistor Embedded Metamaterials Using Variable Resistance

Barrett¹,

Katko²,

Cummer³

2016

PIER

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Abstract-Metamaterials have been previously loaded with diodes and other types of passive circuit elements. Transistors offer an alternative to these established loading elements to expand the possible capabilities of metamaterials. With embedded transistors, additional degrees of freedom are achieved and lay out the architecture for more complex electromagnetic metamaterial design. A mathematical analysis of transistor loaded SRR unit cells is described in which the transistor acts as a variable resistor. From the mathematical analysis, we calculate transmission coefficients for a single unit cell. We then experimentally measure two SRRs with tunable quality factors and thus tunable bandwidth based upon modulating the effective loading circuit resistance to confirm the calculations. From the agreement between the calculated and measured transmission coefficients, we expand the analysis to show that a slab of more densely packed unit cells can achieve negative permeability with varying degrees of dispersion.

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Loss compensation in Metamaterials through embedding of active transistor based negative differential resistance circuits

Cited by 24 publications

References 41 publications

Microwave gain medium with negative refractive index

Microwave gain medium with negative refractive index

Magnetic Field Shielding by Metamaterials

Bandwidth Tuning in Transistor Embedded Metamaterials Using Variable Resistance

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