ELEMENTARY PATTERNS FOR LARGE CONFORMAL ARRAYS.
Item
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Title
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ELEMENTARY PATTERNS FOR LARGE CONFORMAL ARRAYS.
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Identifier
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AAI8023671
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identifier
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8023671
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Creator
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LEE, KANG SOO.
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Contributor
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George Eichman | M. Ettenberg
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Date
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1980
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Electronics and Electrical
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Abstract
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A conformal array under consideration has large number of dipole or slot columns circular symmetrically distributed along the circumference of a conducting cylinder. A dipole or slot column is consisted of infinite number of array elements in the cylinder axial direction. Because of this three dimensional array geometry, beam scan in elevation as well as in azimuth can be carried out. To investigate the beam scan characteristics of these antenna arrays flush-mounted on cylindrical surfaces, the elementary patterns of these arrays are derived.;For a conformal dipole array, the separation between the dipole elements and the conducting surface is within a quarter wavelength and the space between them is filled with a dielectric material, the dielectric constant of which is given as (epsilon). The special case when (epsilon) is equal to (epsilon)(,0), the dielectric constant of the free space, is also studied (Chapter 2). In general, however, the dipole elements can be considered as the printed dipoles on a dielectric board which is clad on a conducting cylinder (Chapter 3). For a conformal slot array, the radiating elements are the open waveguides at the surface of a conducting cylinder which is covered with a thin dielectric sheet (Chapter 4). A dipole or a slot element is activated through a feedline or a waveguide excited by a voltage generator or the waveguide incident field, respectively.;Applying the Watson transform method to the near field calculation around a cylinder circumference, Green's functions that account for the mutual coupling effects between dipole or slot columns can be evaluated. In Chapter 2, the advantage of this complex plane analysis over a direct harmonic series approach is purely its computational efficiency when the radius of an array is large. Additionally, as the dissertation progresses, the complex plane analysis provides physical insight on underlying array behaviors. By investigating the locations of the Watson transform poles on the complex plane and their shifts as functions of various array parameters, the fundamental characteristics of these arrays can be disclosed.;For a conformal dipole array in Chapter 2, the elementary pattern cut on the horizontal plane has a narrow beamwidth compared to the one on the vertical plane determined by the activated column and the cylinder axis. Capitalizing on the broad elevation beamwidth and alleviating the shortcoming of the narrow azimuthal beamwidth with the circular symmetric array geometry, a wide angle beam scan in elevation as well as in azimuth can be carried out.;In Chapter 3 where array elements are the printed dipoles on a dielectric sheet, the Watson transform poles can be found with a perturbation method. Because of mode couplings, as the beam is scanned away from the horizontal plane to the axial direction, new TE poles which include a real pole are emerging in addition to TM poles. Due to a resonance inside the dielectric sheet launched by the emerging real pole, the elementary pattern cut at an elevation angle undergoes significant changes from the horizontal one as the angle is increasing, which ultimately limits the elevation scan of this dipole array.;For the slot arrays in Chapter 4, the roles of TE and TM poles are interchanged from those of Chapter 3. A resonance launched by a real pole results in a dip for the elementary pattern cut on the horizontal plane. As the beam is scanned away, the change in the dip angle can be predicted from the shift of the real pole on the complex plane. For a wide angle elevation scan, because of an additional real pole, multiple resonances take place with accompanying overall changes on an elementary pattern cut. Therefore, the elevation scan must be limited to the onset angle of the multiple resonances.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Engineering
