A Study on Compensation of Rain Attenuation with a Method of Aperture Synthesis Antenna in a Subtropical Zone

作为一种补偿雨衰的方法，我们利用干涉仪的原理，构造了由两个小口径抛物面天线组成的孔径合成天线。用该口径合成天线和其他单根抛物面天线对广播卫星波进行了观测，并对其衰减特性进行了比较。这显示了21dBm的输出功率和(]sy.+-。[)2兆赫/天的频率变化。我们将两个下变频器改造成从外部共同馈送本地振荡器信号，口径合成天线由两个短径为50 cm的偏置抛物面天线组成，基线长度为8m，这是因为我们将口径合成天线与另一个观测组合在一起。比较了两根短径分别为50 cm和75 cm的偏置抛物面天线和一根直径为30 cm的中心馈电抛物面天线，与50 cm单天线相比，综合天线的雨衰性能提高了1.1dB.改进了功率合成器的匹配部分，并对三种单天线在雨强大于10 mm/h时的雨衰特性进行了比较，发现50 cm天线受雨的影响最大，依次为75 cm和30 cm。我们认为这是由天线波束方向图和雨区大小造成的。所以我们建议继续进行详细的观察。如果可以，使用由更多的小口径天线组成的综合天线，例如直径30厘米的抛物面天线，就有必要观测雨衰。

As a method of compensation of rain attenuation, we construct aperture synthesized antenna, which is applied a principle of an interferometer to, consisted of two small aperture parabolic antennas. We have observed Broadcast Satellite wave with that aperture synthesized antenna and other single parabolic antennas, and compared attenuation characteristics.First we made a common local oscillator with a Gunn diode which generates a 10 GHz signal. That shows 21 dBm output power and (]SY.+-。[)2 MHz/day frequency variation. We reconstructed two down converters to be commonly fed a local oscillator signal from the exterior.Aperture synthesized antenna is composed of two offset parabolic antennas, whose short diameter is 50 cm, and has 8 m baseline length because we use aperture synthesized antenna together another observation. Other single antennas which we use for comparison are two offset parabolic antennas, 50 cm short diameter and 75 cm, and one center feed parabolic antenna, 30 cm diameter.In comparison of 50 cm single antenna, the sythesis antenna improves rain attenuation by 1.1 dB.Improving matching section of power combiner, it will be made better.Also among three single antennas, we compare rain attenuation characteristics when rain intensity is over 10 mm/h. We find the 50 cm antenna is most influenced by rain, and in order 75 cm, 30 cm. We think that is caused by antenna beam pattern and rain area size. So we propose to continue an observation in detail. And if we can, using sythesized antenna which is composed of more small aperture antennas, for example 30 cm diameter parabolic antennas, it is necessary to observe rain attenuation.