Unidirectional radiation and, hence, gain enhancement can be achieved by placing a primary radiator (simple antenna) at suitable height over a reflector to diminish back radiation and to enhance the forward radiation. The reflector used to enhance the gain is usually an electrically conducting surface (ECS) or an artificial magnetic conducting surface (AMCS). The ECS unifies the direction of radiation by reflecting the incident wave with [Formula: see text] phase shift, which requires the placement of the antenna at large enough height above the reflector to avoid destructive interference between the incident and the reflected waves. The AMCS is a metasurface constructed as periodic structure to produce reflection with 0° phase. This allows the antenna to be placed near the AMCS without destructive interference. Thus, the combined structure of the antenna and the AMCS reflector can have lower profile than that resulting in the case of employing ECS. The present work proposes a planar wideband antenna as well as an AMCS to produce unidirectional radiation with high gain over a wide frequency band. The proposed antenna is a planar octagon-shaped monopole patch with inverted U-slot and is fed through a coplanar waveguide (CPW). Both the radiating patch and the feeding line are printed on a single-sided substrate of type Rogers RT5880 of dimensions [Formula: see text] and thickness [Formula: see text]. The patch geometry is designed to maximize the radiation efficiency by cutting an inverted U-shaped slot with long base. The proposed AMCS consists of [Formula: see text] cells and has dimensions [Formula: see text]. The metallic patches of AMCS cells are printed on the top layer of a substrate of type Rogers' RO4003C of thickness [Formula: see text]. Both the proposed antenna and AMCS are fabricated for experimental evaluation of the performance of the radiating structure. It is shown by simulation and measurement that the proposed antenna when based on the proposed AMCS produces a realized gain of [Formula: see text] and total efficiency of greater than [Formula: see text] over the frequency band 3.5-6.5 GHz.