الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Drastic modifications of the dipole radiation characteristics are produced by using two plane reflectors intersected at an angle a that is equal to a sub-multiple of1C. The resulting antenna is the well known conventional corner reflector antenna. This type of corner reflectors has been modified by adding a planar conducting plate perpendicular to both the two intersecting conducting plates in such a way that a 3A /4 monopole is used as a feeder element. Many other modifications are applied to the conventional comer reflector antenna.
The most useful radiation patterns of the corner reflector antennas are those in the two principal planes, usually designated by E-plane and H-plane for the conventional corner reflector antennas, and the E-plane and quasi-H plane for the three-dimensional comer reflector antennas.
A drawback of the EMF method is that each wire element , including the feeder element and the images, is assumed infmitesimally thin with a predetennined sine current distribution . This situation differs ftom the practical case where the feeder element has a fmite diameter and the current distribution is not exactly sinusoidal. It is now clear that the’ MOM method can be easily used to obtain the antenna characteristics in this case. The MOM is an effi~ient method. for reducing integral equations governing the current distribution on wire antennas into matrix equations. As soon as we detennine the current distribution alogg the wire s!.gments various characteristics of the analyzed antenna or scatterer are evaluated relatively -easily.
The double comer reflector antenna consists of three intersecting grounded plane conductors and a half wavelength feeder element. An alternative form is also considered by adding two plane conducting sheets at the top and bottom of the antenna reflector are considered. AJso the case of using a 3A14 monopole feeder with grounded plane is considered. The solution for the double corner reflector antenna problem is represented by using the MOM and compared with that for the EMF method. Solid and Grid type reflectors are used to present the antenna reflectors. In the MOM method of analysis all conductors are considered perfect. The active element is fed by a delta- function generator and the current distribution along it is modeled by a seven-degree polynomial. In case of solid conducting sheets, the currents on these sheets are represented by horizontal and vertical components, each in turn is represented by a fmite sum of known functions of unknown coefficients. The MOM method is then used to obtain the input impedance, gain and radiation field components in the two principal planes. It is noticed that the input reactance is nearly positive in all cases.
The effect of adding an upper and lower top plates to the double comer reflector antenna resulted in large fluctuations in the input resistance and reactance with the appearance of side-lobes in the radiation field and this may be verified by saying that the antenna becomes cavity shaped. The effects of eliminating the corner regions of the vertical reflecting planes is also considered. Eliminating the corner regions improve the l’Idiation characteristics of the antenna. It is thus concluded that these regions contribute Uttle in the radiation properties of the antenna. From the results obtained, it is clear that, the double corner reflector antenna is very reliable and of very simple design which allows broadband multi-channel applications in the VHF , UHF and a part of the microwave ftequeocy range.
The MOM is also used to analyze two types, of cylindrical reflector antennas, DII1Dely, the parabolic and hyperbolic reflectors. The surface of each of the reflectors is represeuted by a set of parallel grids, and the feeder element is a half wavelength dipole. The radiation characteristics, input impedance, gain and radiation fields are considered. The effects of changing the frequency on the antenna performance are also considered. The numerical results perfonned on the two curved surface reflector antennas showed that this type of antennas are very promising for the operation in the frequency range from VHF to the end of the SHF frequency range. The analysis of both antennas with the reflectors replaced bya set of parallel grids of suitable dimensions is also reported.
A simple method for synthesizing a feed system for cylindrical reflector antennas working in UHF and VHF frequency ranges is considered. The antenna radiation characteristics are studied using the MOM. The cylindrical reflector is represented by a set of parallel grids. The feeding elements are seven half wavelength dipole. They are located at the caustic of the cylindrical reflector and phased, so that the cylindrical reflector is illuminated in phase. The radiation characteristics, gain and input impedance for different dimensions of the antenna are considered. Also the effects of changing the ftequency and feeding elements locations on the antenna performance are studied. If we increase the number of feeding elements and by tuning the feeding elements phase shift, a sharp beam can be obtained.