Electromagnetic band-gap structures: classification, characterization, and applications
ABSTRACT When periodic structures interact with electromagnetic waves
amazing features result. In particular, characteristics such as
frequency stop-bands, pass-bands and band-gaps could be identified.
Surveying the literature, one observes that various terminology have
been used depending on the domain of the applications. These
applications are seen in filter designs, gratings, frequency selective
surfaces (FSS), photonic crystals and band-gaps (PBG), etc. We classify
them under the broad terminology of “electromagnetic band-gaps
(EBG)”. The focus of this paper is to present a powerful
computational engine utilizing finite difference time domain (FDTD)
technique integrated with the Prony method to analyze and understand the
unique propagation characteristics of different classes of complex EBG
structures such as, (a) FSS structures, (b) PBG crystals, (c) smart
surfaces for communication antenna applications, (d) surfaces with
perfectly magnetic conducting properties (PMC), (e) creation of
materials with negative permittivity and negative permeability, (f)
surfaces with reduced edge diffraction effects, and (g) the notion of
equivalent media. The performance of two types of the EBG structures
namely, single and multi-layered tripod FSS, and rectangular, triangular
and woodpile PBG crystals is detailed. Some of the potential
applications of these structures are highlighted
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ABSTRACT: Reconfigurable frequency-selective surfaces (FSS) composed of ferromagnetic arrays have been fabricated by incorporating MEMS techniques and electrodeposition of highly magnetic materials. These arrays of magnetic microactuators have been demonstrated to dynamically attenuate the frequency bands they were designed for. A single dipole element consists of an 850×158×30 µm 3 ferromagnetic plate made of 40Co-60Ni attached to a pair of 400×5×1 µm 3 double-ended polysilicon torsion bars. The remanent magnetization in the hard ferromagnetic material allows relatively small magnetic fields (~1750 A/m or 22 Oe) to induce significant angular deflections (~45°). By rotating the dipole elements from 0° to more than 45°, the filtering response of the frequency-selective surface can be tuned over a range of 5 GHz at frequencies over 60 GHz.
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ABSTRACT: This paper presents the study of electromagnetic band gap (EBG) structure using slot ring and its effect on circularly polarized triangular patch antenna performance. The EBG structure has been designed on dielectric substrate ε r =4.3 and thickness h=1.53mm. The EBG structure acts as resonator which attenuates the surface wave propagation in a specific frequency range. A new single slot ring EBG structure is proposed which exhibits surface wave attenuation better than 20 dB in the frequency range from 2.75 GHz to 3.2 GHz. An antenna with center frequency of 2.8 GHz is designed with and without EBG. The peak gain and radiation efficiency of this antenna are improved significantly when antenna is above EBG in comparison to antenna without EBG. The simulated radiation patterns of the antenna exhibit reduction in backward radiation when antenna above EBG plane in comparison to radiation pattern without EBG. Keywords-Electromagnetic band gap (EBG), periodic structures, fractal geometry, platting through hole (PTH), microstrip antenna, and surface wave suppression.
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ABSTRACT: Reconfigurable frequency-selective surfaces have been realized by integrating an array of batch fabricated magnetic microactuators into an array of conductive dipole elements. The microactuators in the array consist of a 896×168×30 µm 3 ferromagnetic plate made of 40Co-60Ni attached to a pair of 400×30×1 µm 3 polysilicon torsion bars. The remanent magnetization in the hard ferromagnetic material allows relatively small magnetic fields (~1750 A/m or 22 Oe) to induce significant angular deflections (~45°). By rotating the dipole elements from 0° to more than 45°, the filtering response of the frequency-selective surface can be tuned over a range of 5 GHz at frequencies over 60 GHz.