Physical Bounds and Optimal Currents on Antennas

In English Physical bounds on the directivity Q-factor quotient and optimal current distributions are determined for antennas of arbitrary shape and size using an optimization formulation. A variational approach offers closed form solutions for small antennas expressed in the polarizability of the antenna structure. Finite sized antennas are solved using Lagrangian parameters in a method of moments formulation. It is also shown that the considered stored electric energy can be negative for electrically large objects. This effect is mitigated by a Helmholtz decomposition of the current density. Moreover, it is shown that the optimal charge density for a small antenna can be generated by several current densities. Numerical examples for small and large antennas are used to illustrate the results.