A highly directive dipole antenna embedded in a Fabry-Perot type cavity

We investigate the origin of the directivity of a dipole antenna embedded in a dielectric slab Fabry-Perot cavity. It is shown that the focusing effect is due to the angular selection rules in the Bragg-type mirror and is directly correlated to the frequency selectivity of the cavity. For a 6 GHz resonant device, having a quality factor of 100, the aperture of the beam pattern (E-H plane) is close to 12/spl deg/ in agreement with the arguments based on frequency and angular selectivities. Hence, this kind of cavity could be used in free-space based communication links.