We do not use vector potentials in design. It seems as though they would be useful, but only a few simple antennas fit their direct use. You cannot measure them because they are not physical entities, so they seem artificial. Physical optics (PO) calculates the radiation directly from currents using dyadic Green’s functions but uses long expressions. Nevertheless, many analysis techniques find them more efficient than PO expressions and you should be aware of them. We illustrate their use with a couple of simple antennas.

We use vector potentials to introduce a few antenna concepts. In the first example we apply the magnetic vector potential to calculate the radiation from a short-length current element (dipole) and show how to obtain the pattern. Integration of the radiation pattern power density determines the total power radiated. Because we know the input current and the total radiated power, the ratio of the power to the input current squared gives the radiation resistance. We combine the low radiation resistance with the material resistance to compute the antenna efficiency. Electric vector potentials used with fictitious magnetic currents illustrate analysis by duality. We apply this to the analysis of a small loop and show that it has the same pattern as that of a small dipole.