G

Antenna gain in decibels. G is a scalar or a vector. If G is a vector, each element of G is the gain in decibels of a single antenna.

A

Antenna effective aperture in square meters. The effective aperture describes how much energy is captured from an incident electromagnetic plane wave. The argument describes the functional area of the antenna and is not equivalent to the actual physical area. For a fixed wavelength, the antenna gain is proportional to the effective aperture. A can be a scalar or vector. If A is a vector, each element of A is the effective aperture of the corresponding gain in G.