The Gains, Effective Areas and Equivalent Areas of a Multiport Antenna Array

We review the definitions of 22 parameters of a multiport antenna array operating in a specified direction: 4 excitation-dependent parameters for emission, 10 excitation-independent parameters for emission, and 8 parameters for reception. We concisely set forth their main properties. As examples, we compute and discuss these parameters in the cases of two simple 6-port antenna arrays made of parallel dipole antennas. We investigate the effect of a change of variable describing the excitation during emission. This allows us to find an invariance under a change of excitation variable'', and to compare some of the parameters with the ones used by other authors. We study passive linear embeddings of the MAA ports, to reveal an invariance under an invertible lossless linear embedding’'.