| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 104 === In the thesis, designs of wideband circularly polarized slot antenna which covers the L band (1 GHz ~2 GHz) for Global Positioning System (GPS) applications are proposed. The coplanar waveguide (CPW) fed printed slot antenna has many desirable features like wide bandwidth, ease of fabrication, compact uniplanar configuration, increased freedom for applying perturbations and generating circularly polarization quite efficiently. First we use the Lightening-Shaped feedline and add the perturbation structure at the left side of the slot to design a wide band circular polarization slot antenna. It is found that -10-dB S11 bandwidth and 3-dB axial ratio bandwidth of the antenna are both over 60%.
Slot antennas are generally of bidirectional radiation. In order to achieve the unidirectional radiation, it is usually to apply a ground-plane reflector which is 0.25λ_0 under the antenna. In the thesis, we decrease the height to 0.0625λ_0 by add the slot around the side wall and metal patches around the cavity, and the low profile design has been achieved. With the back cavity, more than 10-dB in front-to-back ratio and more than 3-dB increase in the peak gain haven been obtained, at the price of the decrease in the axial ratio bandwidth.
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