Phase centre of Fabry-Pérot Cavity antennas: Leaky-wave model and analytical formulas

The phase centre of Fabry-Pérot Cavity antennas radiating broadside pencil beams is studied adopting a leaky-wave model of their radiation mechanism. Different definitions are considered for the phase centre, both local, based on curvature properties of the equiphase surfaces in the far field, and global, based on the minimization of suitable functionals of the antenna phase pattern. Analytical formulas are derived for the phase-center location as a function of the relevant leaky-mode attenuation constant and are validated on specific examples of antennas.