Design of bifurcated beam using convex bent array feed for satellite mobile earth station application

Abstract

For multibeam operation at the satellite mobile earth station and telecommunication base stations, a cylindrical lens antenna with multi-feed is a promising candidate due to the simple antenna configuration and good scanning performance to produce multi beams. However, efficient illumination at the lens surface is critical. Previously, the present antennas were used; however, a significant tapered distribution is observed, resulting in underillumination at the lens edges. The feed positions are requested to be placed near the lens to achieve a slender lens form. Therefore, the feed radiation pattern should have high radiations at the wide-angle region. This paper proposes a bifurcated beam array antenna to alter the amplitude distribution. This method is expected to improve the radiation pattern coverage area. In designing a bifurcated beam antenna, the important parameter is to ensure that the separated beams have the same current phase excitations at each radiating element and a precise patch arrangement to achieve the targeted radiation pattern. The differences in surface current will affect the radiation patterns due to the significant interference and cancellation effects which will contribute to high losses. This paper forms the array by a convex bent array with the same phase excitation for all patch elements. The feed performances are also verified by the good agreement between simulated and measured results. An improved aperture distribution is demonstrated for array feed having 0.7λo spacing compared to the tapered distribution by a single patch design with the hyperbolic lens through detailed analysis and comparative study. By changing the spacing distance of the convex bent array, many radiation patterns are observed, such as strong radiation in the wide-angle region, the uniform radiation level in a wide-angle region, and the tapered radiation pattern. Thus, many aperture distributions of center-dip, uniform and tapered, are achieved.