| Summary: | 碩士 === 銘傳大學 === 電子工程學系碩士班 === 102 === The purpose of this thesis is to propose a high-gain dual-band circularly polarized antenna, with two simple steps. First, two dipole antennas are constructed to excite circularly polarized wave in the bands of 2.45 GHz and 5.85 GHz. Then, a frequency selective surface ( FSS ) and a reflecting ground are added to increase the antenna gain in the higher and lower bands, respectively, with little influence on the impedance and axial-ratio bandwidths. The measured data show that the impedance bandwidth is from 2.15 GHz to 3.55 GHz ( 49.12% ) in the lower band, and from 5.41 GHz to 5.98GHz ( 10.01% ) in the higher band. Moreover, the measured axial-ratio bandwidth is from 2.39 GHz to 2.50 GHz ( 4.50% ) in the lower band, and form 5.67 GHz to 5.89GHz ( 3.81% ) in the higher band. With the FSS and a reflecting ground, the antenna gain is increased from 1.23 dB to 7.81 dB in the lower band, and from 2.35 dB to 9.85 dB in the higher band.
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