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''.