| Summary: | 碩士 === 大同大學 === 通訊工程研究所 === 89 === Developments of the DBS (Direct Broadcast from Satellites) operated at the X band have an increasing growth in many countries. The parabolic reflector antennas are commonly used as the received antennas for DBS. Although the gain of the parabolic reflector antennas is over 30dB, the large structure and the curved surface make some troubles in use. The planar reflectarray antennas had been proposed in order to overcome drawbacks of the curved surface. However, large structure and low efficiency still cause problems. In this thesis, we introduce the radial line slot array (RLSA) antennas that can also used for the DBS. They are somewhat similar to a class of slotted waveguide antennas, and the operating frequencies as well as polarization are determined by slots located on special positions. The RLSA not only reduce the size of antennas but also have advantages of high gains and high directivities. This thesis introduces both linearly and circularly polarized RLSA antennas, and have more detailed discussions on gains and other properties of the RLSA fed by the feedhorn. We will also compare with the differences between the RLSA antennas fed by the coaxial cables and the feedhorn.
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