| With the continued development of information technology and the spread of communication business, mobile satellite communications as an important link in the global communication system plays an increasingly important role. At the same time, the upgrading of communication equipment and scarcity of spectrum resources making multi-frequency composite antenna becomes the focus of research project. Helical antenna is widely used in the field of satellite communication with high gain, good circular polarization and other properties. The status of satellite communications antenna and the application prospects of circularly polarized antenna is reviewed in this paper. Then the theory of the helical antenna and composite antenna is summarized.Based on theory of axial mode helical antenna and knowledge of composite antenna, a kind of satellite communication antenna with wideband, high gain, circularly polarized is introduced in this paper. This antenna operates on both UHF and S-band. There are two solutions to achieve dual-band antenna multiplexing-array antenna and nested antenna. After modeling and simulation of software HFSS, the results obtain both programs have a couple of different influences. Array antenna delivers suboptimal performance in all aspects, and it's hard to be improved. Because of simple structure, no feed network losses and improve easily, Nested antenna is a more appropriate design.Finally, an improved nested antenna is designed in this paper. Three measures have been proposed-changing the structure of helical antenna, putting a metal plate on the top of the antenna and changing the structure of floor. Compared with the original antenna, the three antennas increase the gain of 8.4%, 3.2% and 6.3% respectively. Finally, combined with three measures, we designed an improved nested antenna used for both UHF and S-band. It is an antenna with wideband, high gain and circular polarization. And the gain of S-band improved 15.1% compared to the original antenna. |
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