Theory of Thin Antennas
Maxwell's equations for electromagnetic field, which are complemented with boundary conditions on the some of another antenna, allow writing the equation for the current in the conductor of the antenna. Solving it and finding the current distribution along the wire, one can determine the electrical characteristics of a radiator. The power, passing through an antenna surface, does not change in free space and is equal to the power flux in the far region. The vectors of electric and magnetic field strengths are mutually perpendicular. The induced electromotive force (emf) method was proposed in 1922 by Rojansky and Brillouin simultaneously. The theorem about the oscillating power has significantly changed the understanding of the induced emf method, which has been the only way to calculate an antenna input reactance for a long time.