Designs of Compact Circularly-Polarized and Polarization Reconfigurable Antennas by Using Quasi-Lumped Quadrature Coupler

• Main Authors: Ming-Jyun Hou, 侯名峻
• Other Authors: Jeen-sheen Row
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/47490056795937757371

碩士 === 國立彰化師範大學 === 電機工程學系 === 102 === Antennas designs based on a compact feeding network are studied in this thesis. First, three quadrature couplers, including a traditional coupler, a size-reduced coupler, and a quasi-lumped coupler, are designed and their performances are investigated. According to the obtained results, the quasi-lumped quadrature coupler has a relatively narrow operation bandwidth, but it has a much smaller size than the others, which is required for mobile devices of present wireless communication systems. Consequently, two antenna designs based on the quasi-lumped coupler are developed. One is a circularly-polarized square-ring patch antenna suitable for GPS applications. In this design, the coupler is placed in the inner slot of the ring patch, and it is used to simultaneously excite TM01 and TM10 mode of the antenna. From the measured results, the antenna can generate good broadside radiation with right-handed circular polarization at 1.575 GHz; in addition, the 10dB-return-loss and 3dB-axial-ratio bandwidth are 3.9 % and 1 %, respectively. The other design is for polarization reconfigurable antennas which are helpful to reduce the multipath effects. The design adopts a stacked square-ring microstrip antenna, and the polarization switching is realized with a 1 to 4 reconfigurable feeding network composed of the quasi-lumped coupler and several PIN diodes. A prototype that integrates the feeding network into the inner slot of the lower square-ring patch of the stacked patch antenna is constructed. Experimental results show that the prototype can well perform the switching among dual orthogonal linear polarizations and dual orthogonal circular polarizations within a 3.3 % bandwidth centered at 1.98 GHz.