| Summary: | 碩士 === 國立彰化師範大學 === 電機工程學系 === 96 === The designs of circularly-polarized microstrip antennas are investigated in this thesis. The content of the thesis is mainly divided into three parts. In the first part, a conventional single-fed square microstrip antenna with circular polarization (CP) is studied. Several types of the perturbation segments are used to produce the CP radiation, such as using a square patch with a tuning stub or a pair of truncated corners, embedding a cross slot into the radiating patch, and cutting a C-shaped slot on the radiating patch. Their resulting CP performances are numerically analyzed and compared. From the obtained results, it is found that as the microstrip antenna has the same patch size, the antenna gain is decreased with the reducing of the resonant frequency. Therefore, a design method to enhance the gain of the compact microstrip antennas is proposed and studied in the second part of the thesis. The proposed method is using a slotted ground planes, and the measured results show that the antenna gain can be improved by more than 1 dB. In the third part, two designs for a single-fed dual-frequency microstrip antenna with CP operation are exhibited, and they respectively use stacked and single-layer structures to produce dual CP operating frequencies. Details of these designs are described and the obtained experimental results are also presented in the thesis.
Keywords: microstrip antenna, circular polarization, dual frequency operation
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