Summary
International Symposium on Antennas and Propagation
2009
Session Number:3A4
Session:
Number:3A4-2
Design of a Quadratic Backscatter Antenna with Ring Focus Feed
Wanwisa Thaiwirot, Rangsan Wongsan, Monai Krairiksh,
pp.815-818
Publication Date:2009/10/21
Online ISSN:2188-5079
Summary:
Low Earth Orbit Satellite (LEO Satellite) communication systems are one of the new and exciting developments in providing global communication services. Since satellites in low earth orbit change their positions relative to the ground positions quickly, therefore, time required for ground station-satellite communications is limited. Hence, wide beam antennas are needed. At present, the antenna can be used for realizing earth coverage beam in LEO satellite such as shaped reflector antennas. 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, the indoor high speed data transmission: wireless LAN operating in the millimeter wave, attracts considerable attentions [2]. A shaped reflector antenna for 60-GHz indoor wireless LAN access point was developed [3]. However, shaping the reflector to obtain shaped beam becomes complicated. This yields a discontinuous surface and more complicated manufacturing process. Thaivirot et al. [4] 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 ellipse 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. The proposed antenna will be installed on the centre point of ceiling in the large hall and can illuminate a predefined circular area for all users without substantial spatial variation as shown in Fig.2. Physical theory of diffraction (PTD) is utilized for analysis and design. The input parameters of the proposed antenna are derived in closed form.