Small-Size Circular Patch Antenna Using a Cross Slot with Unequal Slot Lengths

Circularly polarized waves can be obtained from patch antennas when a square patch is excited by two feeds, with their inputs having a 90° phase shift. A new, circularly polarized small-size micro strip antenna using a proximity coupled feed method is proposed. A simple configuration based on a cross slot with unequal slot lengths on a circular patch is adopted to realize a small-size element antenna. The proposed antenna has no 90° hybrid coupler for circular polarization. The measured results verify the circular polarization, and the antenna radius was reduce by about 22% by using the slot lengths which are nearly equal to the diameter of the circular patch antenna. Good impedance and axial ratio characteristics have been obtained.