摘要: An important consideration which must be taken into account in the formulation and design of any radar system is the degradation in the signal-target information introduced by the atmosphere. The propagational effects which are pr... 展开 An important consideration which must be taken into account in the formulation and design of any radar system is the degradation in the signal-target information introduced by the atmosphere. The propagational effects which are prevalent when radio waves traverse the atmosphere manifest themselves as refractive bending,time delays,Doppler errors,rotation of the plane of polarization (Faraday effect) and attenuation. In addition,the presence of celestial radio noise sources such as the sun and radio stars are capable of reducing the overall system sensitivity. Auroral and meteoric ionization at ionospheric heights,and the moon also introduce interference and clutter problems. These phenomena are described and assessed with application to frequencies in the VHF and UHF range. The calculations which are presented are based on a normal static,undisturbed atmosphere. Atmospheric anomalies brought about by man-made artificial devices are not considered. 收起