| In recent years, with the rapid development of wireless communication, the role of satellite navigation and positioning system in the production and life of human society becomes more and more important. After years of research and development, China's Beidou satellite navigation system is being built and gradually put into use. In addition to its use in the military field, Beidou satellite navigation system has been developed rapidly in the civil field, especially in both the vehicle navigation system and the portable mobile terminal Positioning System. Therefore, the research of the terminal antenna in the satellite positioning system is of great value and significance, especially the multi-frequency technology and miniaturization technology of the antenna. Suitable for the satellite terminal antenna form various, in many antenna forms, four-arm spiral antenna because has the good wide beam circularly polarization characteristic, the good low elevation angle gain and the easy realization miniaturization and so on the merit, is suitable uses in the satellite navigation system the terminal antenna. In order to meet the requirements of high integration of satellite navigation system, the miniaturization and multi-frequency technology of the four-arm helical antenna and the miniaturization and broadband technology of the Feed network are studied in this paper.The details of this article are as follows:First of all, this paper briefly describes the development and research status of Beidou satellite positioning system, and enumerates several common antenna structures and their respective features which can be used as satellite terminal antennas, including four-arm helical antennas, microstrip antennas, and so on. This paper summarizes the relevant literatures,introduces the history and development of the four-arm spiral antenna, introduces the basic stricture and radiation mechanism of the four-arm spiral antenna, and provides a sufficient theoretical basis for the design of the antenna.Secondly, based on the structure analysis and theoretical research of the four-arm helical antenna, a traditional air-loaded four-arm helical antennas are designed, and the simulation and modeling of the antenna are described in detail, and the effect of the performance of the Feed network on the circular polarization performance of the four-arm helical antenna is also illustrated.Then, a miniature printed conformal four-arm spiral antennas with air loading were designed,its working frequency is Beidou 2nd B1 frequency band (1561.098MHZ), in order to realize the miniaturization of the antenna, this paper has carried on the miniature design to the antenna spiral arm and the feed network respectively, the antenna height is 40mm, the spiral diameter is 25.65mm.Finally, the design of a small-scale, dual-frequency four-arm spiral antenna based on Double-layer feed network loading, compared to the general air loaded four-arm spiral antenna,the overall size of the antenna designed in this paper is very low: the height of only the other.27mm, the spiral diameter is 65mm. In this paper, the detailed process of antenna design is given,and the influence of the antenna structure on its dual frequency characteristics and radiation characteristics is analyzed. |
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