Abstract: In this paper a novel circular-polarized microstrip patch antenna is given based on the study of common circular microstrip patch antenna. This new type of patch looks like common circular patch with some slots. Numerical results and measured data indicate that the new patch antenna has a wide beam and good performance of axial ratio. The radiation pattern of the antenna is very good. Another property of the new patch antenna is that the size of new antenna is smaller than common circular patch or annular patch antenna.