A rectangular microstrip antenna over a metasurface is proposed for circularly polarized radiation across wide frequency range. The proposed antenna comprises a rectangular microstrip radiator, a metasurface with 7 £ 7 unit cells, and a coaxial feed probe. The prototype antenna with an antenna volume of 78mm x 60mm x 4.8mm achieves a circularly polarized bandwidth (3-dB axial ratio) of 19.5% (3.7 GHz-4.5 GHz), VSWR · 2 bandwidth of 34.2% (3.4 GHz-4.8 GHz) with maximum gain of 7.4 dBic.