一种高极化纯度低溢出的圆对称天线设计
A Circularly Symmetric Antenna Design With High Polarization Purity and Low Spillover
摘要：
我们描述了两个圆对称天线的发展，具有高极化纯度和低溢出。这两个卫星都被设计用于5 GHz的全天空偏振和强度调查（C波段全天空调查，C-BASS）。测量要求极低水平的交叉极泄漏和远侧旁瓣。两个不同的现有天线，6.1米和7.6米直径的初级，通过更换饲料和次级光学适应，导致在0.73度FWHM相同的波束性能，交叉极化优于-50 dB，和远出旁瓣低于-70 dB。通过使用对称的低损耗介质泡沫支撑结构用于次镜，避免了对次支撑支柱的需要，实现了偏振纯度。通过在主镜和次镜周围使用吸收挡板，以及使用低旁瓣轮廓波纹喇叭天线，大大减少了地面溢出。6.1米的天线和接收机已经完成，测试结果表明，光学满足其设计目标。
英文摘要：
We describe the development of two circularly symmetric antennas with high polarization purity and low spillover. Both were designed to be used in an all-sky polarization and intensity survey at 5 GHz (the C-Band All-Sky Survey, C-BASS). The survey requirements call for very low levels of cross-polar leakage and far-out sidelobes. Two different existing antennas, with 6.1-m and 7.6-m diameter primaries, were adapted by replacing the feed and secondary optics, resulting in identical beam performances of 0.73deg FWHM, cross-polarization better than -50 dB, and far-out sidelobes below -70 dB. The polarization purity was realized by using a symmetric low-loss dielectric foam support structure for the secondary mirror, avoiding the need for secondary support struts. Ground spill-over was largely reduced by using absorbing baffles around the primary and secondary mirrors, and by the use of a low-sidelobe profiled corrugated feedhorn. The 6.1-m antenna and receiver have been completed and test results show that the optics meet their design goals.
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