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本文论述将大口径偏置天线用作地面站天线时的实用化问题及其解决办法,并叙述实际设计试制的孔径为11.5米的偏置卡塞格伧天线的结构与电气特性。一般说来,采用镜面修整法虽能以高效率获得低旁瓣等特性,但本文所介绍的天线是修整副反射镜和聚焦反射镜,这样便降低了主反射镜的成本。另外,为得到低旁瓣特性而研究了广角方向特性恶化的因素与改善方法。实测说明,该天线的孔径效率在76%以上(20干兆赫频带),广角方向特性过丈的轴对称天线相比改善了5~10分贝,并指出反射镜反射板间隙引起的绕射是广角方向特性恶化的重要因素。由于主反射镜采用水平设置减轻了夭线的风负荷,以及限定了天线的驱动范围使天线结构简易轩帚化,因而有可能架设在件通的电话局屋顶上。
This paper discusses the practical problems and solutions of using the large aperture biased antenna as a ground station antenna, and describes the structure and electrical characteristics of a biased Cassegrain antenna with a hole diameter of 11.5 meters. In general, although the use of mirror dressing method with high efficiency to obtain low sidelobes and other characteristics, but the antenna described in this article is to trim the secondary reflector and focusing the reflector, thus reducing the cost of the primary reflector. In addition, the factors that worsen the characteristics of the wide-angle direction and the improvement methods have been studied to obtain low sidelobe characteristics. The measured results show that the aperture efficiency of the antenna is improved by more than 76% (20 megahertz) and the axial symmetry of the wide-angle direction is improved by 5 ~ 10 dB compared with that of the axial symmetry antenna. It is also pointed out that the diffraction caused by the reflector reflector gap is wide angle An important factor in deteriorating the directional characteristics. The use of a horizontal reflector at the main reflector reduces the wind load on the antenna and limits the drive range of the antenna to make the antenna structure easier and more likely to be erected on the phone’s roof.