Summary
International Symposium on Antennas and Propagation
2010
Session Number:4FA4
Session:
Number:4FA4-4
A Quadratic Backscatter Antenna with Ring Focus Feed
Wanwisa Thaiwirot, Rangsan Wongsan, Monai Krairiksh,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
In the modern world of telecommunications, the concept of wireless global coverage is of the utmost importance. Only satellite system can achieve real global coverage. Recently, low earth orbit satellite (LEO satellite) communication systems are exciting development for applications where a short round trip time such as mobile satellite service. Because the coverage area provided by a single LEO satellite only covers a small area that moves as the satellite travels at the high angular velocity needed to maintain its orbit. Many LEO satellites are needed to maintain continuous coverage over an area. Thus, an antenna on the satellite must have a wide beamwidth in order to provide more time for ground station-satellite communication. Shaped beam reflector antenna has become key element of communication satellites having requirement of irregular shaped coverage area. The highly shaped-beam antenna was first developed to give approximately uniform coverage of the earth from satellite antenna [1]. Recently, the similar requirement but different application, a shaped reflector antenna for 60-GHz indoor wireless LAN access point was developed [2]. However, shaping the reflector to obtain shaped beam becomes complicated. This yields a discontinuous surface and more complicated manufacturing process. Thaivirot et al. [3] presented the synthesis of radiation pattern of variety of the shaped backscatters antenna. It was found that, the quadratic backscatter will provide the appropriate characteristics. Therefore, it is suitable for using as an antenna for realizing earth coverage beam in LEO satellite application as shown in Fig.1. To improve gain and efficiency of reflector antenna, the displaced-axis dual reflector antenna was discussed. It was found that the axially displaced ellipse (ADE antenna) provides an excellent choice for compact high-gain spacecraft antenna applications. As a result, this paper presents the axially displaced ellipsoid antenna. The proposed antenna is a centrally fed displaced axis quadratic backscatter antenna with a ring focus feed. A backscattering technique is used with the main reflector to achieve wide beamwidth for earth coverage in LEO satellite. Moreover, this approach is fruitful for high-gain antenna applications, especially for Wireless Local Area Network (WLAN) large-scale indoor base station as shown in Fig.2. Physical theory of diffraction (PTD) is utilized to analyze the radiation pattern of proposed antenna and verified with the experimental result