OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS ANTENNA LAB
A study is described of the antenna noise char-ACTERISTICS DUE TO THERMAL NOISE GENERATED BY HOT OBJECTS EXTERNAL TO THE ANTENNA AND FED INTO THE ANTENNA THROUGH THE ELECTROMAGNETIC FIELD. Information was obtained that can be used to design antennas with improved signal-to-noise ratios. Thermal noise characteristics of an antenna are not unique, but are a complex function of environment and orientation as well as pattern, and so must be investigated for each individual antenna with respect to its particular location and application. This investigation was only concerned with a parabolic reflecting antenna over flat terrain with the main beam pointed vertically upwards. Methods of decreasing received thermal noise, and hence increasing the gain-to-noise ratio, by shielding are presented. A novel type of Cassegrain feed is also discussed as a possible means of obtaining more desirable illumination of the main aperture.