چكيده به لاتين
Leaky wave antennas are among the most widely used antennas over the past few decades. Some of the attractive features of these antennas such as frequency scanning capability of the beam, high gain and high efficiency, wideband performance and the ability to control of the side lobe levels are attractive to antenna designers. In order to control the side lobe levels, a simple and step by step design method for these antennas has been presented in this dissertation. By design and construction of a prototype antenna, the usefulness of this method has been illustrated. For the air filled rectangular waveguide with single mode operation, it has been shown that the maximum scanning angle of the beam from the broadside axis is 60৹. For scanning of the beam near the endfire region, the use of ridged rectangular waveguide as the guiding structure of the antenna is proposed. Based on proposed designed method, a single ridge rectangular waveguide leaky wave antenna has been designed and fabricated. For this antenna the scanning angle of 70 degree from broadside has been achieved in simulation and measurement. In most applications, in order to prevent corrosion, degradation, heat transfer and etc, it is necessary to cover the external surface of the antenna with a dielectric coating. Therefore, the study of the effect of dielectric coating on the radiation characteristics of these antennas is necessary. In this thesis, the effects of dielectric coating with the extended finite ground plane on the radiation properties of the leaky wave antenna have been investigated. The coating has been lead to unwanted ripples with pattern rotation in the E-plane. In the H plane, the maximum of the beam slightly moves toward the endfire and for the beams in the endfire region the gain is reduced significantly. In the following, by investigation of the dielectric coating on the radiation patterns of a small leaky wave antenna, for surface wave reduction and compensate the coating effects on the radiation patterns, a simple and efficient method has been proposed. It is shown that the amplitude of the surface wave can be reduced by using conductor posts around the slot before reaching the dielectric edge. These posts which can be implemented as mechanical rivets help us eliminating the ripples from the E-plane pattern. The proposed method has been implemented on three leaky wave antennas with Teflon coating. Finally, simulated and measured results for the antennas are presented and discussed.
