Maximum power penetration through an electrically small aperture

An analysis is presented for the maximum power absorbed by a monopole antenna over a ground plane with a load impedance receiving an external time-harmonic field. The power conservation law is examined in the cases of total or partial absorption of the field power, noting the necessity for the antenna and the electrical field to be parallel and 90 deg out of phase to have a maximized interaction. Consideration of the maximal absorption area leads to a discussion of the EM penetration through an electrically small aperture, which yields an expression for the maximal EM absorption area, as well as the transmission cross-section.