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A synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

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dc.contributor.authorSmith, William Travisen
dc.contributor.committeechairStutzman, Warren L.en
dc.contributor.committeememberBrown, Gary S.en
dc.contributor.committeememberDavis, William A.en
dc.contributor.committeememberKlaus, Martinen
dc.contributor.committeememberPratt, Timothy J.en
dc.contributor.departmentElectrical Engineeringen
dc.date.accessioned2014-03-14T21:15:39Zen
dc.date.adate2007-07-10en
dc.date.available2014-03-14T21:15:39Zen
dc.date.issued1990en
dc.date.rdate2007-07-10en
dc.date.sdate2007-07-10en
dc.description.abstractSurface errors on parabolic reflector antennas degrade the overall performance of the antenna. They cause amplitude and phase errors in the aperture field which lower the gain, raise the side lobes, and fill in the nulls. These are major problems in large ->space reflector antenna systems. F or example, future multiple beam antenna systems requiring spatial isolation to allow frequency reuse could be rendered useless if high side lobes are present. Space antenna structures are difficult to build. They must maintain a nearly perfect parabolic shape in a harsh environment while remaining lightweight. The restrictions on the structure become more severe as science and technology requirements demand electrically large antennas. Mechanically, there are technologies [4)r building antennas with adaptive surfaces that can compensate for many of the larger distortions caused by thermal and gravitational forces. However, as the frequency and size of the reflectors increase, the subtle surface errors become significant and degrade the overall radiation pattern. It is for this reason that another method must be used to further improve the radiation pattern. Electromagnetic compensation for surface errors in large apace reflector antennas has been the topic of several research studies. Most of these studies try to correct the focal plane fields of the reflector near the radiation pattern. The compensation is implemented by weighting the elements of an array feed. In most of the studies, a precise knowledge of the reflector surface is required. An alternative approach to electromagnetic compensation is presented in this study. The proposed technique uses pattern synthesis to compensate for the surface errors. It differs from previous methods in two major respects. The previous studies used global algorithms that try to correct the entire focal plane field near the focal point or the aperture plane field and, hence, modify the entire radiation pattern. The pattern synthesis approach uses a localized algorithm in which pattern corrections are directed specifically towards portions of the pattern requiring improvement. The second major difference is that the pattern synthesis technique does not require knowledge of the reflector surface, but instead uses radiation pattern data to perform the compensation.en
dc.description.degreePh. D.en
dc.format.extentviii, 248 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-07102007-142513en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07102007-142513/en
dc.identifier.urihttp://hdl.handle.net/10919/38744en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1990.S643.pdfen
dc.relation.isformatofOCLC# 23460019en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1990.S643en
dc.subject.lcshAntennas (Electronics) -- Mathematicsen
dc.subject.lcshAntennas, Reflectoren
dc.subject.lcshSpace frame structuresen
dc.titleA synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennasen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineElectrical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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