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Author

Silvio Hrabar

Other affiliations: Brunel University London
Bio: Silvio Hrabar is an academic researcher from University of Zagreb. The author has contributed to research in topics: Metamaterial & Antenna (radio). The author has an hindex of 19, co-authored 168 publications receiving 1579 citations. Previous affiliations of Silvio Hrabar include Brunel University London.


Papers
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Journal ArticleDOI
TL;DR: In this article, a rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability was investigated both theoretically and experimentally, and it was shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus it can be considered as a dual of the ordinary waveguide.
Abstract: A rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability is investigated both theoretically and experimentally. It is shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus, it can be considered as a dual of the ordinary waveguide. The transversal dimension of this waveguide can be arbitrarily smaller than half of a wavelength in the filling material, provided that the transversal permeability is negative. This peculiar behavior may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides loaded with double ring resonators in 7 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave passband located below the cutoff frequency. Furthermore, it was experimentally shown that the increase of the physical length of the waveguide caused the decrease of the electrical length. This is a direct proof of the backward-wave propagation since the phase of the backward wave increases along the waveguide.

288 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental demonstration of the overcoming of basic dispersion energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported.
Abstract: Experimental demonstration of the overcoming of basic dispersion-energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported. The experimental metamaterial operates in RF regime, and it is based on air transmission line loaded with negative capacitors. Measurement results clearly show almost dispersionless Epsilon-Near-Zero behavior, accompanied with superluminal both phase and group velocities, over a bandwidth of more than four octaves (2 MHz-40 MHz). The principle of periodic loading of transmission line with negative capacitors may find applications in ultra-broadband active metamaterials for antennas and cloaking technology.

112 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown both numerically and experimentally that the basic dispersion constraints of any passive medium might be overcome by using an active transmission line-based metamaterial.

95 citations

Journal ArticleDOI
TL;DR: This communication studies the stability of several networks with non-Foster reactive elements by using a time domain approach to model more realistic situations for antenna and metamaterial technology.
Abstract: During the last couple years there have been lot of attempts to use negative non-Foster reactive elements for improving the bandwidth of electrically small antennas (ESAs) or metamaterial-based structures. However, negative non-Foster reactive elements are actually electronic circuits that are not absolutely stable, which could impose serious problems in practical applications. This communication studies the stability of several networks with non-Foster reactive elements by using a time domain approach. This will help to model more realistic situations for antenna and metamaterial technology.

89 citations

Journal ArticleDOI
TL;DR: In this paper, a polarization converting metasurface that operates in the X-band was designed and fabricated by cascading three patterned metallic sheets in order to achieve the desired polarization conversion and high reflection.
Abstract: A polarization converting metasurface that operates in the ${X}$ -band is designed and fabricated. The metasurface converts a linearly polarized incident electromagnetic wave to an orthogonal polarization upon reflection. The design has a subwavelength thickness of 1.27 mm (0.04 $\lambda $ ), a half-power bandwidth of 22%, and a polarization conversion ratio of 99.4%. The metasurface was fabricated with a low-cost printed circuit board process. It is realized by cascading three patterned metallic sheets in order to achieve the desired polarization conversion and high reflection. The polarization conversion is accomplished by guiding and coupling electromagnetic energy between pairs of orthogonal slots in a ground plane, placed at the edges of each unit cell. The performance of an experimental prototype showed close agreement with simulation.

68 citations


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Posted Content
TL;DR: The two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.
Abstract: We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

1,587 citations

01 Jan 2016
TL;DR: The electrodynamics of continuous media is universally compatible with any devices to read and is available in the book collection an online access to it is set as public so you can get it instantly.
Abstract: Thank you for reading electrodynamics of continuous media. Maybe you have knowledge that, people have look numerous times for their chosen books like this electrodynamics of continuous media, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their computer. electrodynamics of continuous media is available in our book collection an online access to it is set as public so you can get it instantly. Our book servers saves in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the electrodynamics of continuous media is universally compatible with any devices to read.

898 citations

Journal ArticleDOI
TL;DR: This work demonstrates a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow.
Abstract: Sensing an incoming signal is typically associated with absorbing a portion of its energy, inherently perturbing the measurement and creating reflections and shadows. Here, in contrast, we demonstrate a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow. This unique sensing device is based on the unusual scattering properties of a parity-time (PT) symmetric metamaterial device formed by a pair of electro-acoustic resonators loaded with suitably tailored non-Foster electrical circuits, constituting the acoustic equivalent of a coherent perfect absorber coupled to a coherent laser. Beyond the specific application to non-invasive sensing, our work broadly demonstrates the unique relevance of PT-symmetric metamaterials for acoustics, loss compensation and extraordinary wave manipulation.

605 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the transverse-magnetic (TM) wave interaction with a pair of slabs, one being an epsilon negative (ENG) layer in which the real part of permittivity is assumed to be negative while its permeability has positive real part, and the other being a mu-negative (MNG) layer that has the real parts of its permittability negative but its permitivity has positivereal part.
Abstract: Here, we analyze the transverse-magnetic (TM) wave interaction with a pair of slabs, one being an epsilon-negative (ENG) layer in which the real part of permittivity is assumed to be negative while its permeability has positive real part, and the other being a mu-negative (MNG) layer that has the real part of its permeability negative but its permittivity has positive real part. Although the wave interaction with each slab by itself has predictable features, we show that the juxtaposition and pairing of such ENG and MNG slabs may, under certain conditions, lead to some unusual features, such as resonance, complete tunneling, zero reflection and transparency. The field distributions inside and outside such paired slabs are analyzed, and the Poynting vector distributions in such structures are studied. Using equivalent transmission-line models, we obtain the conditions for the resonance, complete tunneling and transparency, and we justify and explain the field behavior in these resonant paired structures. Salient features of the tunneling conditions, such as the roles of material parameters, slab thicknesses, dissipation, and angle of incidence are discussed. The analogy and correspondence between the ENG-MNG pair and the pair of a slab of conventional material juxtaposed with a "double-negative" medium is also discussed. Finally, a conceptual idea for a potential application of such a "matched" lossless ENG-MNG pair in "ideal" image displacement and image reconstruction is proposed.

555 citations