ABSTRACT This paper is presenting two different microstrip antennas (LHCP and RHCP antennas). It can explain the effects of S-shape and Z-shape slots for left-hand circular polarization and right-hand circular polarization respectively. Both types of slots are used to convert linear polarized antenna into the circularly polarized antenna. It is simulated with the help of CST-2015 and HFSS2018 design software. The antenna is designed into two steps. At first step, a simple linear microstrip antenna is designed and with second step, slots are used for circular polarization. The operating simulated frequency in both types of software’s is 0.258 THz to 0.355 THz and having 11 % operating bandwidth with the axial ratio at 3 dB. All the results of both antennas are the same but only radiation patterns results are opposite in polarization. The paper also presents the parametric study of copper material thickness and substrate thickness of the antenna.