Bandwidth performance limits for finite antennas

Bounded bandwidth performance measures are defined for any finite antenna, either in free space or above a perfectly conducting ground plane. The measures are valid for any class of antenna, for example, for patch antennas, dielectric resonator antennas and so on, the radiating currents of which can be confined to the Chu sphere or hemisphere of radius a. The performance bounds are believed to be nearly achievable for electrically small antennas. Examples are given for a loop antenna and a patch dipole antenna, where the former is electrically small and the latter has dimensions comparable to a wavelength.