الفهرس 
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Abstract
This thesis consists of six chapters organized as follows:
Chapter one is an introduction to the underlying concept of log-periodic dipole array (LPDA) as a broadband wire antenna, with two modified versions: The log-periodic resonant V-array (LPV-array) and the cross-element LPDA It shows that the aim of the present work is to maximize the gain performance by providing the antennas with ” suitable giddied-type wire reflectors.
Chapter two gives a survey on the method of moments (MOM) for the analysis and design of arrays of wire antennas; taking into account the Numerical Electromagnetics , Code (NEC).
Chapter three presents the design of two antennas of log-periodic structure with 70° gridded-type corner reflector. One antenna is 9-element LPDA of 5: I desired bandwidth and the other is 5-element LPDA of 1.52: I desired bandwidth. Results of gain over an isotropic radiator, radiation patterns and input impedance as a function of frequency are included.
Chapter four is a study of 5-element LPV -array to cover the UHF range (300-3000) MHz with relatively compact size. This array has to be fed with the 70° gridded-type corner reflector to improve its radiation characteristics.
Chapter five describes the antenna gain and polarization of two cross-element LPDA with 10 elements. and 18 elements, each fed with a gridded-type planar reflector. A short review of wave and antenna polarization is presented,
Chapter six contains the conclusions of the thesis. As main conclusions we can extract the following:
1. The 9-element LPDA alone and with corner reflector retain the freqllcncyindependent behavior throughout the operating bandwidth. With corner reflector the antenna yields higher gain peaks that reach 12.7 dB at 500 MHz. It gives, as a whole, 2.4 to 6.4 dB rise in gain.\
2. The 5-element LPDA fed corner reflector is rendered to be a compact antenna of broad bandwidth and pronounced better gain than that of the 5-element LPDA alone. It extends the bandwidth to (250-850) MHz rather than (300-450) MHz and yields gain peaks that reach 15.57 dB at 700 MHz.
3. The 5-element LPV-array alone (10: I bandwidth) is improved in gain at higher operating modes (f > 1350 MHz) and the addition of corner reflector yields pronounced peaks on the gain curve that can attain 14.5 dB at 3000MHz .