Physical limitations on D/Q for antennas

In English In this paper, physical limitations on the directivity D and Q-factor Q are derived for antennas of arbitrary shape. The quotient D/Q is shown to be bounded from above by the antenna volume and certain shape coefficients in terms of the eigenvalues of the high-contrast polarizability dyadic. The theory is exemplified by numerical results for the half-wave antenna with astonishing agreement.