On Maximum Bandwidth of Rectangular Cavity Antennas With Broadside Radiation Pattern

Physical limitations on bandwidth of aperture antennas backed by a small rectangular cavity are investigated here. To this purpose, theoretical bound on maximum bandwidth is studied using the scattering approach introduced by Gustafsson et al. As the approach was mainly applied to wire antennas and metallic scatterers, we extend it to aperture antennas and validate the formulation by comparing analytical and numerical results. We concentrate on cavities in an infinite ground plane with aperture dimensions smaller than half of the free-space wavelength.