EM Coupling Between Two Multiport Antenna Systems

Perhaps the most famous consequence of reciprocity in EM theory is that the transmitting and receiving patterns of an antenna system are, subject to certain conditions, fully equivalent. This property is widely applied to a typical antenna pattern measurement configuration in which the (test) antenna, whose EM radiation characteristics are measured, acts as a receiver of the signal transmitted from the (stationary) referential antenna. A necessary condition for such measurements to be successful is the property of reciprocity of the corresponding transfer impedance. This chapter analyzes the transfer impedance matrix and its properties with the aid of reciprocity theorems of both the time‐convolution and time‐correlation types. In accordance with standard network theory, EM coupling between two such linear and time‐invariant antenna multiport systems can be described in terms of network parameters.