In this paper, we design an implementable high-performance flat reflector based on conformal transformation optics. In the proposed 2-dimensional device, the rescaling refractive index approach is applied to overcome the sub-unit refractive index issue, resulting in an all-dielectric isotropic graded-index medium that is physically implementable. Rotating the permeability profile around the antenna axis yields the 3-dimensional profile of the flat reflector construction. The dielectric with continuous refractive index profile is split into eleven layers with a constant refractive index. The proposed antenna requires only dielectric layers with the permittivity of 1.1 to 3.8, making it realizable. Simulation results show that the proposed flat reflector can operate in wide frequency bandwidth. The simulated antenna gain is about 25.27 to 29.55 dBi in the 13-30 GHz frequency range with the side-lobe level below -15 dB. Design and simulation of the proposed antenna are done using COMSOL Multiphysics, and simulation results are validated with CST Studio Suite.