The design of a periodic leaky-wave antenna for angle-of-arrival (AoA) estimation is presented. Thanks to multiple radiating space harmonics, a multibeam operation is achieved in order to scan a large angular range with a limited fractional frequency bandwidth. The matching and radiation efficiency issues raised by the large spatial period involved with multibeam operation is addressed by using a dedicated unit-cell to control both the leakage constant and the Bloch impedance. Simulations confirm that a MUSIC processing enables the system to perform AoA estimation without ambiguity among the multiple beams. This allows for AoA estimation over the 180°-angular range with a bandwidth of only 3.7% at 27 GHz