ABSTRACT-Circularly polarized (CP) antennas are widely used in modern wireless communication systems because of their immunity to multipath distortion and polarization mismatch losses. On the other hand, unidirectional radiation patterns are generally desirable since they can provide larger signal coverage and stabilize the signal transmission. As a result various Omni directional CP antennas have been proposed and investigated over the past few years. The design utilizes two monopole modes of a circular patch which connects to a modified ground plane by a set of conductive pins, to achieve wide-band impedance matching. The curved branches introduced at the edge of circular ground plane excite a degenerate mode and create CP fields. To verify the design, a prototype should be fabricated operating at 2.4GHz-WLAN band and measured reflection coefficient, radiation pattern, and antenna gain should agree well with simulation results. In this paper simulation carried out using arlonAD320A instead of RogersRT/duroid 5880 because cost of Rogers material is very expensive. But losses in arlon material are more. The losses are reduced by decreasing number of shorting pins and increase the radius of shorting pins. The prototype as a low profile 0.024 0 , a return loss value30dB and a antenna gain of 4.68dB. To further characterize the design concept, a parametric study of the antenna is carried out using HFSS.