A two-dimensional leaky-wave antenna (2-D LWA), also known as a Fabry-Perot cavity antenna, is a planar structure consisting of a grounded dielectric slab with a partially reflecting surface (PRS) on top. It is commonly fed with nondirective sources (such as dipoles) to obtain a directive pattern. For instance, a narrow pencil beam at broadside can be obtained by feeding a 2-D LWA with a simple horizontal electric or magnetic dipole type of source. A periodic array of metallic patches, strips, or slots (forming a planar FSS) is often used to form the PRS.