| Antennas and antenna arrays are vital in electronic warfares. In order to achieve high gain and beam scanning, antennas should work in the form of arrays. In modern radar and electronic warfare's applications, the ability of scanning wide of radars and antennas (arrays) are required. To achieve the aim, the beamwidth of antenna elements of array should be broadened. However, the 3dB beamwidth of the typical microstrip antenna's E plane and H plane are less than 100°. Therefore, it is necessary to design microstrip antenna with broad beamwidth.The feed network guarantees the magnitude and phase distributions among antenna elements in the antenna array. Therefore, the performance of the feed network plays an important role in the overall performance of the antenna array. Series feed network is small in size and fewer discontinuous in energy transmission and less in insertion loss. Its disadvantage is that the feed line will brings phase difference among the output ports. Thus, even phase distributions in a wide frequency range can hardly achieved.This thesis firstly introduces the composite right/left handed transmission line (CRLH-TL) with metamaterial characters into the design of feed network. By taking advantage of the CRLH-TL's large phase constant, the phase difference introduced by traditional transmission lines can be compensated. Therefore, the phase balance is achieved among the antenna elements in a certain frequency range. Good agreements between the experiment results and simulation results validate the proposed design. After that, a broad-beamwidth antenna is designed, whose 3dB beamwidth of the E plane and H plane are enlarged to 130°and 160°, respectively. Finally, based on board-beamwidth microstrip antenna arrays and CRLH-TL feed networks, a wide scanning antenna array in Ku-band is designed. In the present design, the antenna shadow can be overcome to a certain extent and the scanning range can be broadened to±60°. |
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