A high gain and broadband circularly polarized antenna is designed with a single planar layer substrate. To realize a broadband antenna initially, a circular patch antenna is fed by a slot with a coplanar feed line in the ground plane. A metasurface is designed to consist of a 3 × 3 array of circle patches with the circular patch antenna at the center of the array. Moreover, the slot is also modified into L-shape to generate circular polarization. In addition, stubs are introduced in the slot to improve the impedance bandwidth. As a result, the circular patch metasurface has improved the impedance bandwidth, axial ratio bandwidth and gain. Due to the above-mentioned combinations, an impedance bandwidth of 20.18% (4.9–6 GHz) with an axial ratio bandwidth of 16.21% (5.1–6 GHz) is obtained. Furthermore, the antenna has a peak gain of 10.43 dBic which is remarkably very high in single-layered planar antennas.