Dual-band circularly polarized monopole antenna for WLAN applications

A novel planar dual-band monopole antenna with circular polarization (CP) operation is proposed. By appropriately introducing dual strip-sleeves shorted at the ground plane, the proposed dual-band CP design can easily be achieved with the impedance bandwidth (RL □10 dB) of about 266 / 980 MHz and the 3 dB axial-ratio (AR) bandwidth of about 103 / 700 MHz for 2.4 / 5.2 GHz wireless local area network (WLAN) applications. The measured peak gain and radiation efficiency are about 4.1 / 3.3 dBic and 94 / 84 % across the operating bands, respectively, with nearly bidirectional patterns in the XZ- and YZ-planes.