| Summary: | 博士 === 國立中山大學 === 電機工程學系研究所 === 88 === The designs of various feeding networks for microstrip antennas have been investigated in this dissertation. In the active microstrip antenna designs, an amplifier-type microstrip antenna integrates a two- port amplifier circuitry to the various passive antennas through a 50Ω inset microstrip feed line which can function in broadband operation，CP operation and dual-frequency operation. As for the broadband circularly polarized microstrip antenna with a dual-perpendicular feed design, antenna with a dual-perpendicular feed which was formed by a Wilkinson power divider with a quarter-wavelength section of microstrip line for providing equal splitting of the input power and 90° phase difference to the two feed points has been presented. The broadband CP bandwidth can be achieved due to the good isolation between the two output lines of the feed network. In the microstrip antennas with CPW feed designs, we first proposed a microstrip antenna with three-dimensional CPW feed. A separate feed substrate is used which can provide a large-area space for the layout of complicated microwave circuitry. In addition, the feed substrate can also be oriented to the patch substrate with various angles, resulting in more flexibility in the proposed three-dimensional feed design. Finally, we proposed a design with two slot lines located at both sides of the coupling slot which can lengthen the excited patch surface current path, thus the resonant frequency is reduced and an antenna size reduction up to 40% has been obtained.
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