Determination of the Generalized Scattering Matrix of an Antenna From Characteristic Modes

A method to determine the generalized scattering matrix of an antenna using characteristic modes is presented. When the characteristic currents flowing at a feed point, the radiation patterns of the characteristic currents, and the eigenvalues are known, the generalized scattering matrix can be calculated. It is shown that an antenna whose behavior is dominated by a single characteristic mode becomes a minimum scattering antenna. The formula is verified using a two wavelength dipole antenna and a bow-tie antenna.