The Principle of Reciprocity in Antenna Theory

The reciprocity theorem is applied to transmitting and receiving antenna systems in order to establish several important relationships. Formulas are deduced which establish a relation between the receiving current and power of any given antenna and the field intensity of the arriving waves, all the parameters entering into the formulas being the parameters of the same antenna when it is used as a transmitting antenna. It is shown that, in the case of strong interference, (1) the highest possible directivity is of importance both in the transmitting and in the receiving antennas and (2) the efficiency and the coefficient of exploitation of the receiving antenna are of no importance. In the case of low interference, it was found that, (1) the directivities of both the receiving and transmitting antennas are of equal importance and (2) the efficiency and coefficient of exploitation of the receiving antenna are just as important as the efficiency of the transmitting antenna.