This paper presents a 1×3 antenna array composed of a radiator and a reflector. The radiator consists of three series feeding circular patches etched with slots. Coplanar waveguide feeding is adopted to obtain ultra-wide bandwidth. The radiator is printed on a flexible substrate of polyimide with thickness of 70µm. A ground plane is arranged under the radiator to obtain directional radiation. The total size of the proposed antenna is 94mm×26mm×25.07mm. The proposed antenna's simulated bandwidth of is 3.19-20 GHz.