| Summary: | 碩士 === 國立彰化師範大學 === 電信工程研究所 === 104 === In this thesis, we propose two different types of antennas design. The first is the multiband planar antenna using slots and the second is a novel method of radiation characteristics improvements for conical horn antenna.
The multiband planar antenna using slots is designed to be used for hotspots applications of 4G (LTE) and Wi-Fi. We use the asymmetrical conductor-backed finite-ground coplanar waveguide as the basic architecture and also acts as the main RF signal transmission path. The slots with different lengths and widths are placed in parallel with each other on the top and bottom ground planes to make multiple resonances at different frequencies, and therefore, to meet the broadband requirement. These slots are also used to control the current directions and thus, to determine a special characteristic mode that always radiate in the broadside direction for all working bands. In addition, the use the partial side wall, which act as a short path, can adjust the antenna input impedance and current directions for lower frequency band.
Second, we consider the pyramidal horn antenna used as the primary feed of the reflector antenna of satellite communication systems. To meet the requirements of lower sidelobes, symmetrical and resemble radiation patterns for E-plane and H-plane, we propose a new method to improve the radiation characteristics of the feed horn. We arrange a metal cone in the central axis of the pyramidal horn antenna and the slope of this metal cone is nearly the same as that of the feed horn. The phase center point of the feed horn due to this inserted metal cone changes very little so that the relation distance between the reflector and this associated feed horn nearly the same.
Finally, we will demonstrate our design methods and the measurement and simulation results are also discussed.
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