S. Yarga

The Ohio State University, Columbus, OH, United States

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Publications (15)8.64 Total impact

  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: In this paper, the authors analyze the receiving and transmitting patterns of Hertzian dipoles embedded within magnetic photonic crystal (MPC) unit cell ensemble. The authors demonstrate that a rather thin MPC assembly achieves unidirectional radiation with non-reciprocal receiving/transmitting patterns. The authors also propose a simpler unit cell structure to realize the phenomena.
    Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: A new small antenna formed by a periodic assembly of two-tone dielectrics (Barium-titanate and Alumina) emulating an anisotropic medium is presented. Directive radiation characteristics are achieved when operated close to the band edge frequencies of a class of anisotropic photonic crystals supporting degenerate band edge (DBE) modes. Unique aspects of the antenna design are its smaller size (0.79 lambda<sub>0</sub> times 0.80 lambda<sub>0</sub> times 0.28 lambda<sub>0</sub>) and nearly optimum aperture efficiency. The subject 3-D assembly, fed by a slot on a ground plane, achieved a directivity of 10.17 dBi. This communication presents the design of the 3-D assembly using full-wave simulations and provides experimental verification of the overall antenna performance.
    IEEE Transactions on Antennas and Propagation 04/2009; · 2.33 Impact Factor
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: A multilayer rectangular dielectric resonator antenna (DRA) operating at a new hybrid mode is presented. The DRA is formed by a dispersion engineered combination of isotropic/anisotropic dielectric layers. These layers are optimized to operate at a degenerate band edge (DBE) mode with the introduction of misaligned anisotropic layers. A prototype DBE-DRA antenna is realized by emulating the anisotropic medium with a periodic assembly of two-tone dielectrics (barium-titanate and alumina).
    IEEE Antennas and Wireless Propagation Letters 02/2009; · 1.67 Impact Factor
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: In recent years, there is a growing interest in compact high-gain antennas with a single feed for civil/tactical wireless communication systems. Electromagnetic band-gap (EBG) structures with embedded antennas/feeds present an attractive solution due to their high directivity and feeding ease. EBGs have been used to obtain highly directive radiation in two forms: (a) as a substrate utilizing defect resonances (Brown et al., 1993) (b) as a host medium near the band edge frequencies (Bulu et al., 2003). The first group requires comparatively large physical sizes for practical applications (e.g. thicknesses of larger than lambda<sub>o</sub>/2). For the latter, one must be careful to operate at the Fabry-Perot (F-P) transmission peak closest to the band edge. The degenerate band edge (DBE) resonances (see Fig. 1c) are of this type, but also have the unique property of exhibiting narrower F-P peaks in the vicinity of the band edge leading to better directional selectivity (Figotin and Vitebskiy, 2006). Consequently, DBE crystals can achieve required levels of high directivity using fewer number of unit cells, resulting in low profile structures.
    Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: We present an experimental demonstration of the degenerate band edge (DBE) behavior in anisotropic photonic crystals. Specifically, we present the design of a DBE crystal using a full-wave analysis method, its realization using laminate layers of printed strips emulating anisotropy, and experimental verification of field amplitude growth using field probe measurements. Although the DBE and magnetic photonic crystal theory has been presented before, this work is the first experimental demonstration of such anisotropic assemblies.
    IEEE Transactions on Antennas and Propagation 02/2008; · 2.33 Impact Factor
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    ABSTRACT: We present a 3-D design and realization of degenerate band edge (DBE) periodic assemblies forming anisotropic photonic crystals to achieve highly directive radiation characteristics when operated close to band edge frequencies. For the design, we employ a method of moments implementation of the surface integral equation in presence of uniaxial dielectric materials using closed form dyadic Green's functions. To our knowledge, this is the first time that closed form uniaxial dyadic Green's functions are used in a surface integral equation formulation. The proposed method of moments implementation is then adapted to design DBE crystals using an engineered composition of Barium-titanate and Alumina platelets. This paper points out the computational challenges associated with the DBE antenna design procedure.
    Computational Electromagnetics Workshop, 2007; 09/2007
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: Electromagnetic band-gap (EBG) structures have been used to realize highly directive antennas either by using them as substrates and utilizing defect resonances or as a host medium when operating near band edge frequencies. As an alternative, it was recently proposed that degenerate band edge (DBE) crystals can achieve the required resonances using fewer number of unit cells, resulting in low profile structures.
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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    S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: Periodic arrangements of metallo-dielectric structures have been shown to exhibit novel phenomena that can be exploited for microwaves. Among them, regular band edge (RBE) structures are known for their high Q properties, and left handed materials lead to much smaller phase shifters and couplers. More recently, a new class of periodic arrangements, referred to as magnetic photonic crystals (MPCs) and degenerate band edge crystals (DBEs) have been shown to significantly improve matching of the incoming fields and support slow wave phenomena (frozen modes) leading to very large wave fields within the crystal over a relatively wide bandwidth. Thus, they can be used for much greater sensitivity antennas. In this paper, we experimentally demonstrate for the first time the support of such phenomena using a newly designed crystal from very low cost materials. We demonstrate that the purported slow wave and high amplitude phenomena can be observed using on periodic cells with a finite aperture. These experiments are corroborated with numerical data, making the utilization of these new class crystals for high gain and narrow beam scanning antennas a practical possibility.
    Antennas and Propagation Society International Symposium 2006, IEEE; 08/2006
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    ABSTRACT: Photonic crystals have been the subject of extensive research for almost twenty years. More recently, the physical nature of the constitutive components was diversified to include anisotropic, magnetic, metallic, and nonlinear materials. Greater diversity of physical properties, along with more sophisticated space arrangement of the constituents, can result in qualitatively new features and novel phenomena, such as electromagnetic unidirectionality and the frozen mode regime. The resulting structures are referred to as magnetic photonic crystals (MPCs). This presentation provides analysis that demonstrates the benefits and potential applications of MPCs and degenerate bandgap structures (DBEs) from a numerical and experimental point of view. Three dimensional realizations of antennas and conformal arrays within MPCs are presented using frequency domain and time domain techniques, and preliminary experimental data are given for validation purposes
    Antennas and Propagation Society International Symposium 2006, IEEE; 08/2006
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    ABSTRACT: First Page of the Article
    Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on; 02/2006
  • S. Yarga, K. Sertel, J.L. Volakis
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    ABSTRACT: Summary form only given. Magnetic photonic crystals (MPCs) display exotic propagation characteristics in the form of a frozen mode (Figotin, A. and Vitebskiy, I., Phys. Rev. E, vol.63, 066609, p.1-17; Phys. Rev. B, vol.67, 165210, p.1-20). At microwave frequencies, ferrites are associated with losses which are further exacerbated due to resonant wave behavior (frozen mode) within the crystal. To minimize losses, it is therefore necessary to minimize the ferrite layer thickness while still attaining sufficient Faraday rotation to preserve the frozen mode phenomenon. We investigate the performance of: (1) chiral inclusions within a ferrite medium; (2) chiral (handed) ferrite inclusions within a possibly non-magnetic host medium. Our preliminary analysis demonstrates that much thinner periodic MPC layers can be designed using chiro-ferrite layers. Concurrently, the MPC frozen mode and reflectivity properties are maintained. More specifically, the inflection point in the band diagram is achievable using only a fraction (lower than 1%) of the original ferrite material, implying a significant loss reduction in practice.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    ABSTRACT: New magneto-photonic assembly designs for high-gain antennas require dielectrics with a significant anisotropy and low loss at GHz frequencies. This paper describes an approach to fabricate such dielectrics from ceramic laminates. These laminates consist of two ceramics with largely different permittivities and low dielectric losses. Alternating layers of commercially available α-Al2O3 and Nd-doped BaTiO3 were laminated using organic adhesives. Equivalent permittivity tensors and loss tangents were characterized using a resonant cavity-based approach, which was coupled with a finite-element method full-wave solver. Measured permittivity values were in good agreement with mean field predictions; a minimum loss tangent 1.1×10−3 was obtained when using one-component epoxy (Loctite®-3982) adhesive. Application of two-component epoxy (M-bond 610) adhesive results in a slightly higher loss but better mechanical properties and machinability. These laminates were used to demonstrate high gain in a prototype antenna with 6 misaligned anisotropic dielectric layers.
    Journal of Materials Science 43(5):1505-1509. · 2.31 Impact Factor
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  • Dissertation, Salih Yarga