Studies on Dual-Broadband Circularly Polarized Monopole Antennas

• Main Authors: Jhen-Hong Lin, 林震鴻
• Other Authors: Chung-I. G. Hsu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/28739903281054796462

碩士 === 國立雲林科技大學 === 電機工程系碩士班 === 101 === This thesis presents a broadband and a dual-band circularly polarized (CP) printed monopole antenna design for GNSS and INMARSAT systems, as well as a back cavity design which is used to improve the antenna gain. Through a few simple design steps starting from a basic monopole antenna which does not have circular polarization characteristics originally, the designed CP monopole antenna having a small radiator size can achieve a 3-dB axial-ratio bandwidth more than 35.2%. In addition, on the basis of the broadband CP monopole antenna mentioned above, we have also developed two dual-band CP monopole antennas with their dual-band frequency ratios controllable. For the antenna with its two CP bands created using a band-notch mechanism, the achieved dual-band frequency ratio is low. For the other with its two CP bands created by moving the upper portion of the wide CP band toward a higher frequency, the resulting dual-band frequency ratio is slightly higher. Finally, in order to improve the antenna gain, we put a back cavity with metal sidewalls behind the monopole antennas. It can not only reduce the backward radiation by more than 20 dB but also increase the antenna gain by more than 6 dBic.