Abstract: In this paper, a microstrip patch antenna is proposed to achieve circular polarization diversity. Stubs are addedaround two sides of the rectangle patch and connected by PIN diodes. By turning the diodes on and off, the phase difference of twoorthogonal modes is changed, which lead to the novel antenna can radiate with either left hand circular polarization (LHCP) orright hand circular polarization (RHCP) using the same feeding probe. The voltage standing wave ratio (VSWR) and axial ratio(AR) values are less than 2 and 3dB respectively in (2800±10)MHz frequency range. The simulated and measured results bothvalidate the proposed design process.