A novel configuration of a circularly polarised (CP) reconfigurable aperture antenna is presented. In a number of recent studies, some new and promising designs for circularly polarised cavity-backed antennas with a parasitic patch have been proposed to obtain circular polarisation and unidirectional radiation properties. However, these designs still have the disadvantage of producing single polarisation. To overcome this disadvantage, a reconfigurable antenna using pin diodes is proposed. By combining the reconfigurable aperture antenna with a parasitic patch and a low profile cylindrical cavity and optimising the antenna parameters, a high gain antenna with significantly improved impedance and axial ratio bandwidths can be achieved.