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- Creators: Palais, Joseph
Description
Articially engineered two-dimensional materials, which are widely known as
metasurfaces, are employed as ground planes in various antenna applications. Due to
their nature to exhibit desirable electromagnetic behavior, they are also used to design
waveguiding structures, absorbers, frequency selective surfaces, angular-independent
surfaces, etc. Metasurfaces usually consist of electrically small conductive planar
patches arranged in a periodic array on a dielectric covered ground plane. Holographic
Articial Impedance Surfaces (HAISs) are one such metasurfaces that are capable of
forming a pencil beam in a desired direction, when excited with surface waves. HAISs
are inhomogeneous surfaces that are designed by modulating its surface impedance.
This surface impedance modulation creates a periodical discontinuity that enables a
part of the surface waves to leak out into the free space leading to far-eld radia-
tion. The surface impedance modulation is based on the holographic principle. This
dissertation is concentrated on designing HAISs with
Desired polarization for the pencil beam
Enhanced bandwidth
Frequency scanning
Conformity to curved surfaces
HAIS designs considered in this work include both one and two dimensional mod-
ulations. All the designs and analyses are supported by mathematical models and
HFSS simulations.
metasurfaces, are employed as ground planes in various antenna applications. Due to
their nature to exhibit desirable electromagnetic behavior, they are also used to design
waveguiding structures, absorbers, frequency selective surfaces, angular-independent
surfaces, etc. Metasurfaces usually consist of electrically small conductive planar
patches arranged in a periodic array on a dielectric covered ground plane. Holographic
Articial Impedance Surfaces (HAISs) are one such metasurfaces that are capable of
forming a pencil beam in a desired direction, when excited with surface waves. HAISs
are inhomogeneous surfaces that are designed by modulating its surface impedance.
This surface impedance modulation creates a periodical discontinuity that enables a
part of the surface waves to leak out into the free space leading to far-eld radia-
tion. The surface impedance modulation is based on the holographic principle. This
dissertation is concentrated on designing HAISs with
Desired polarization for the pencil beam
Enhanced bandwidth
Frequency scanning
Conformity to curved surfaces
HAIS designs considered in this work include both one and two dimensional mod-
ulations. All the designs and analyses are supported by mathematical models and
HFSS simulations.
ContributorsPandi, Sivaseetharaman (Author) / Balanis, Constantine A (Thesis advisor) / Palais, Joseph (Committee member) / Aberle, James T., 1961- (Committee member) / Trichopoulos, Georgios (Committee member) / Arizona State University (Publisher)
Created2017
Description
Since the advent of High Impedance Surfaces (HISs) and metasurfaces, researchers
have proposed many low profile antenna configurations. HISs possess in-phase reflection, which reinforces the radiation, and enhances the directivity and matching bandwidth of radiating elements. Most of the proposed dipole and loop element designs that have used HISs as a ground plane, have attained a maximum directivity of 8 dBi. While HISs are more attractive ground planes for low profile antennas, these HISs result in a low directivity as compared to PEC ground planes. Various studies have shown that Perfect Electric Conductor (PEC) ground planes are capable of achieving higher directivity, at the expense of matching efficiency, when the spacing
between the radiating element and the PEC ground plane is less than 0.25 lambda. To establish an efficient ground plane for low profile applications, PEC (Perfect Electric Conductor) and PMC (Perfect Magnetic Conductor) ground planes are examined in the vicinity of electric and magnetic radiating elements. The limitation of the two ground planes, in terms of radiation efficiency and the impedance matching, are discussed. Far-field analytical formulations are derived and the results are compared with full-wave EM simulations performed using the High-Frequency Structure Simulator (HFSS). Based on PEC and PMC designs, two engineered ground planes are proposed.
The designed ground planes depend on two metasurface properties; namely in-phase reflection and excitation of surface waves. Two ground plane geometries are considered. The first one is designed for a circular loop radiating element, which utilizes a
circular HIS ring deployed on a circular ground plane. The integration of the loop element with the circular HIS ground plane enhances the maximum directivity up to 10.5 dB with a 13% fractional bandwidth. The second ground plane is designed for a square loop radiating element. Unlike the first design, rectangular HIS patches are utilized to control the excitation of surface waves in the principal planes. The final design operates from 3.8 to 5 GHz (27% fractional bandwidth) with a stable broadside maximum realized gain up to 11.9 dBi. To verify the proposed designs, a prototype was fabricated and measurements were conducted. A good agreement between simulations and measurements was observed. Furthermore, multiple square ring elements are embedded within the periodic patches to form a surface wave planar antenna array. Linear and circular polarizations are proposed and compared to a conventional square ring array. The implementation of periodic patches results in a better matching bandwidth and higher broadside gain compared to a conventional array.
have proposed many low profile antenna configurations. HISs possess in-phase reflection, which reinforces the radiation, and enhances the directivity and matching bandwidth of radiating elements. Most of the proposed dipole and loop element designs that have used HISs as a ground plane, have attained a maximum directivity of 8 dBi. While HISs are more attractive ground planes for low profile antennas, these HISs result in a low directivity as compared to PEC ground planes. Various studies have shown that Perfect Electric Conductor (PEC) ground planes are capable of achieving higher directivity, at the expense of matching efficiency, when the spacing
between the radiating element and the PEC ground plane is less than 0.25 lambda. To establish an efficient ground plane for low profile applications, PEC (Perfect Electric Conductor) and PMC (Perfect Magnetic Conductor) ground planes are examined in the vicinity of electric and magnetic radiating elements. The limitation of the two ground planes, in terms of radiation efficiency and the impedance matching, are discussed. Far-field analytical formulations are derived and the results are compared with full-wave EM simulations performed using the High-Frequency Structure Simulator (HFSS). Based on PEC and PMC designs, two engineered ground planes are proposed.
The designed ground planes depend on two metasurface properties; namely in-phase reflection and excitation of surface waves. Two ground plane geometries are considered. The first one is designed for a circular loop radiating element, which utilizes a
circular HIS ring deployed on a circular ground plane. The integration of the loop element with the circular HIS ground plane enhances the maximum directivity up to 10.5 dB with a 13% fractional bandwidth. The second ground plane is designed for a square loop radiating element. Unlike the first design, rectangular HIS patches are utilized to control the excitation of surface waves in the principal planes. The final design operates from 3.8 to 5 GHz (27% fractional bandwidth) with a stable broadside maximum realized gain up to 11.9 dBi. To verify the proposed designs, a prototype was fabricated and measurements were conducted. A good agreement between simulations and measurements was observed. Furthermore, multiple square ring elements are embedded within the periodic patches to form a surface wave planar antenna array. Linear and circular polarizations are proposed and compared to a conventional square ring array. The implementation of periodic patches results in a better matching bandwidth and higher broadside gain compared to a conventional array.
ContributorsAlharbi, Mohammed (Author) / Balanis, Constantine A (Thesis advisor) / Aberle, James T (Committee member) / Palais, Joseph (Committee member) / Trichopoulos, Georgios C (Committee member) / Arizona State University (Publisher)
Created2020