US Patent 9279845 Antenna characterization in a waveguide

A method for determining at least one characteristic of an antenna requiring: a) positioning an antenna in a space surrounded by a waveguide; b) feeding an electric excitation signal (utx(t)) into a feed connection of the waveguide; c) receiving the electric response signal (urx(t)) emitted by the antenna resulting from the excitation signal (utx(t)); d) determining at least one characteristic of the antenna from a portion of the response signal (urx(t)) and a corresponding portion of the excitation signal (utx(t)), where the portion of the response signal (urx(t)) is evaluated in the time domain and satisfies the following conditions: (i) only one or more waves of the electromagnetic field caused by the excitation signal (utx(t)) and running from the feed connection towards the antenna exist at the location of the antenna; and (ii) the electromagnetic field at the location of the antenna is a TEM field.