This paper introduces a single-feed dual-band antenna for an anti-jam global positioning system array. The antenna is composed of a circularly polarized (CP) crossed scythe-shaped dipole over a finite artificial magnetic conductor (AMC) reflector. The dual-band operation is obtained by utilizing the original band generated by the radiator and an additional band caused by surface waves propagating on the finite AMC. The compact radiating system, including the crossed dipole and the finite AMC surface, is backed by a cavity to achieve a wide CP radiation beamwidth and a high level of mutual coupling at both bands.