Circular polarization (CP)designs of circular and rectangular microstrip patch antennas are demonstrated. Proximity coupled feed and aperture coupled feed methods are used. The proposed CP designs are achieved by implementing a suitable crossslot either on the patch (in the case of proximity coupled feed method) or on the ground plane (in the case of aperture coupled feed method), which results in excitation of two near degenerate orthogonal modes of near equal amplitudes and 90。 phase difference. Attempts are made to change the geometry of slots' ends to introduce a novel structure in order to achieve a better matching performance.
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