Crescent-cut and Extended Circular Patch Circularly Polarized Microstrip Antenna for ISM Band Wireless Applications

Four circularly polarized single feed microstrip patch antennas are introduced in this paper. Circular polarization is achieved by a single crescent-cut, a single crescent extension, a double crescent-cut and a double crescent extension on a circular patch antenna. All four antennas are designed to operate in the Industrial, Scientific and Medical (ISM) band. The antennas are designed and simulated to obtain parameters by an electromagnetic simulation tool named ADS (Advanced Design System). The return loss of the single crescent-cut antenna is -20.58 dB, the single crescent extension is 16.95 dB, the double crescent-cut is -34.98 dB and the double crescent extension is -31.47 dB between 2.35 GHz to 2.45 GHz that show good input impedance matching. The axial ratios are found less than 3 dB in their resonance frequencies. Smith charts of these antennas have a dip at 2.4, 2.38, 2.42 and 2.42 GHz respectively demonstrating the ability to achieve circular polarization within the frequency range of the ISM band signifies the capability of this system. Performance analyses based on different parameters of the four antennas have been done at the end.