In this letter, a novel fixed-frequency scanning antenna is proposed. The antenna consists of a grounded substrate-superstrate configuration covered with a two-dimensional periodic array of slots in a conducting plate, fed by a simple source (e.g., a narrow slot on the ground plane); the superstrate is a thin ferroelectric slab that, under a bias voltage, changes its permittivity allowing for a fixed-frequency electronically controlled scanning process. The operating principles of such an antenna are illustrated and numerical results are provided to show the attainable performance with actual ferroelectric materials.