N. Herscovici

Air Force Research Laboratory, Washington, Washington, D.C., United States

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Publications (8)1.18 Total impact

  • Boris Tomasic, Naftali Herscovici, Hans Steyskal
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    ABSTRACT: A metamaterial slab of Wire-Split Ring Resonators was analyzed focusing on physical aspects. Effective constitutive parameters were extracted vs. number of W-SRR layers in the slab. We have shown that a minimum of 8 layers is required to accurately characterize the bulk metamaterial properties. Losses, spatial dispersion, and mode conversion in the unit cell are also discussed. I. INTRODUCTION
    01/2011;
  • B. Tomasic, H. Steyskal, N. Herscovici
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    ABSTRACT: In this paper the dyadic Green's function and expressions for the fields due to an electric current source in a Floquet phase-shift-wall waveguide (unit cell) are derived. The expressions are valid in the entire unit cell region including the source. Numerical results for the scattering from a conducting strip in a unit cell using these expressions are in a good agreement with numerical results obtained by the HFSS code. The dyadic Green's function can be used in future analyses of phased arrays and metamaterials.
    Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
  • B. Tomasic, N. Herscovici
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    ABSTRACT: We have developed an accurate analysis of a cylindrical array structure of long slots with connected dipole feeds. The array exhibits wide-band characteristics, about 3:1 frequency band at broadside scan. The code we generated could be used to accurately predict the impedance and radiation characteristics of the array.
    Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
  • N. Herscovici, B. Tomasic, J. Ginn, T. Donisi
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    ABSTRACT: In this paper a new type of a wideband aperture-coupled microstrip antenna is presented. The antenna is modelled as a 2.5 D structure, and is optimized using a genetic algorithm (GA). In addition to the radiator shape, the feed and the coupling slot dimensions are also included in the optimization process. The impedance bandwidth corresponding to VSWR<2:1 achieved by this optimization for the microstrip fed case is slightly larger than 38% and slightly above 20% for the stripline fed case. In order to achieve this bandwidth with traditional aperture-coupled patch, a multilayer patch structure is required. The concept proposed here, considerably reduces the complexity of the fabrication process.
    Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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    ABSTRACT: It is seen that for each dielectric constant there is a set of frequencies for which the antenna is operational. The lowest frequency would be inversely proportional to the square root of real part of the dielectric constant for an infinite dielectric. For the finite dielectric, the decrease in frequency was about 80% of that for the infinite dielectric. Thus, it is seen that even a small amount of dielectric material, in which the antenna is immersed, reduces the operational frequency significantly. It is interesting to note that the ratios of the frequencies for each dielectric constant are almost identical. Therefore, if the lowest frequency of operation is known, the higher frequencies of operation can be easily calculated. We note that the antenna is reasonably well matched, except at some of the mid frequencies.
    Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
  • N. Herscovici, B. Tomasic, J. Ginn, T. Donisi
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    ABSTRACT: The scanning characteristics of a certain class of Aperture Coupled Fed Fragmented Microstrip Antennas are presented. This type of antenna exhibits relatively wide-band performance and its scanning characteristics are investigated.
    01/2009;
  • B. Tomasic, N. Herscovici, H. Steyskal
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    ABSTRACT: We have presented an accurate analysis for the array structure of long slots with dipole feeds as described in Lee et al. (2006). The array exhibits wide-band characteristics, about 3:1 frequency band, with the above specified geometrical parameters. The code we generated could be used to optimize the performance of the element in an infinite array environment.
    Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
  • Naftali Herscovici, James Ginn, Tony Donisi, Boris Tomasic
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    ABSTRACT: This paper summarizes an effort to obtain a wideband aperture-coupled fragmented microstrip antenna. The antenna is modeled as a 2.5D structure, and is optimized using a genetic algorithm (GA). The realistic physical feed, a microstrip-fed slot, is also included in the optimization process.
    01/2008;