| Summary: | 碩士 === 國立臺南大學 === 電機工程學系碩博士班 === 103 === A novel coplanar-waveguide (CPW)-fed monopole antenna with dual-band circular polarization (CP) has been demonstrated in this work. A simple two-finger fork-like strip monopole, which is fed at the CPW feeding line, is designed to resonate at the 1.57 GHz; in addition, the resonant mode also excites a right-hand circularly polarized (RHCP) wave for applications of the global positioning system (GPS). A rectangular patch is added at the end of one finger to generate a horizontal current component, thus enhancing the CP performance. A left-hand circularly polarized (LHCP) wave at 2.33 GHz for the satellite digital audio radio (SDAR) service system is excited by modifying the geometry of the ground plane. To improve the CP performance at the SDAR band, a short stub is added at the left side of the ground plane. Only two resonances are merged and then a moderate impedance bandwidth is obtained. The measured impedance bandwidth of a reflection coefficient (S11) < -10 dB ranges from 1.49 to 2.92 GHz, and thus covers most of the commercial wireless communication systems. The 3-dB axial ratio (AR) bandwidths are about 40 MHz at the lower band (1.57 GHz) and 290 MHz at the upper band (2.33 GHz).
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