A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a flat reflector is designed and presented. The measured bandwidth of the antenna is about 1.8 % (5.32 -5.52) while the simulated bandwidth is 1.11% (5.32 -5.44 GHz). A comprehensive parametric study has been conducted to realize the effects of slot size, slot position and reflector parameters to increase the directivity of the designed antenna. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.