Measurement of antenna parameters
In Chapter 3 we discussed the mathematical description of the radiation characteristics of the reflector antenna, and we treated the influence of aberrations (defocus situations) and other errors in Ch. 4. In radio astronomy the purpose of the telescope, the reflector antenna in our discussion, is to collect radiation from the celestial source as a function of position on the sky, frequency, polarisation and sometimes time. In order to draw conclusions about the source of radiation, we need to establish the relationship between the parameters describing the physical processes in the source and those of the receiving antenna. Thus we must develop a mathematical formulation for the interaction between the transmitting cosmic radio source (or satellite, etc) and the receiving radio telescope, the reflector antenna discussed sofar. As we have seen earlier, the characteristics of the latter are described by the spatial radiation characteristic, which we have called the antenna pattern. By virtue of the reciprocity theorem the pattern of a transmitting antenna is identical to that of a receiving antenna. (Silver, Ch. 2.13, 1949). We have already introduced terms like main beam and sidelobes of the antenna pattern.
KeywordsBrightness Temperature Radio Source Angular Size Error Pattern Surface Error
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