CPW‐fed sqaure ring slot antenna with circular polarization radiation for WiMAX/WLAN applications

The design of a small size 50 × 50 mm2coplanar waveguide‐fed square ring slot antenna is studied. To attain circular polarization (CP) radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the worldwide interoperability for microwave access 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and wireless local area network 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending a C‐shaped branch from the vertical monopole is proposed. Good impedance matching and CP performance was achieved by further extending a vertical tuning strip from the C‐shaped branch. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 63.89% and 7.93% were achieved. Furthermore, stable gain variation of approximately 2.7 dBic and radiation efficiency of more than 85% were also exhibited across the bands of interest.