| Summary: | 碩士 === 國立彰化師範大學 === 電機工程學系 === 96 === This thesis presents the designs for reconfigurable microstrip antenna. Three types of the reconfigurable antenna are studied. The first one is a circularly-polarized (CP) microstrip antenna capable of switching polarisation sense. The microstrip antenna is excited by an open-loop microstrip line through the coupling of a ring slot in the ground plane. The polarisation diversity is achieved by using a pair of pin diodes to reconfigure the flowing path of the current on the open-loop microstrip feed line. The measured results show the 3dB-axial-ratio bandwidth of more than 10 % can be obtained at the two polarisation senses. The second one is a CP reconfigurable microstrip antenna with dual-frequency operation. The antenna has a square radiating patch, and each side of the square patch is connected a shorting wall via a diode. By switching the four diodes, the CP operating frequency of the antenna can be varied. Several prototypes of the reconfigurable dual-frequency antennas with different frequency ratios were fabricated. The last one is a CP reconfigurable microstrip antenna with polarization and frequency diversities. The antenna is excited through the coupling of a cross slot with unequal lengths. Two diodes are used to reconfigure the radiating patch, and by controlling the states of the diodes, the polarization sense of the antenna can be switched between left-hand and right-hand CP. Moreover, the two CP modes are operated at different frequencies. An antenna prototype was also implemented and the obtained results are shown.
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