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1.引言在射电天文学中,交替地使用初级激励器、用于宽带测量的普通抛物面反射器,其孔径效率一般为55％-68％。孔径效率主要取决于孔径的遮挡系数(Aperturverblockung),例如Effelsberg无线电望远镜天线的遮挡系数为17％。如果象卡塞格伦天线、格雷高里天线那样,利用一般的初级(原文为‘次级’一译者注)激励器(锥形喇叭,双模喇叭)同样也能得到55—68％的孔径效率。当第三级方向图(主反射器)的旁瓣衰减是够大时,利用同轴辐射器或波纹喇叭(在这种波纹喇叭里,通过喇叭内部的波纹结构而产生HE11波形)也能提高孔径效率。波纹喇叭作为初级激励器有下述优点:
1. INTRODUCTION In radio astronomy, primary actuators are alternately used for general parabolic reflectors for wideband measurements, with aperture efficiencies typically ranging from 55% to 68%. The aperture efficiency depends mainly on the aperture blocking factor (Aperturverblockung), for example the Effelsberg radio telescope antenna has a blocking factor of 17%. If, like the Cassegrain and Gregorian antennas, the same primary (cone, bimodal) exciter is also used, 55-68% of the Aperture efficiency. When the sidelobe attenuation of the third-order pattern (the main reflector) is large enough, the use of a coaxial radiator or a corrugated horn (in which the HE11 waveform is generated by the corrugated structure inside the horn) can also be increased Aperture efficiency. Corrugated horn as a primary actuator has the following advantages: