Compact CPW-Fed Dual-Band Linearly and Circularly Polarized Monopole Antenna for WiMAX and WLAN

A compact dual-band linearly and circularly polarized monopole antenna employs an inverted L-shape and an asymmetric ground plane fed by a coplanar waveguide (CPW). The inverted L-shape strip produces an orthogonal component in the ground plane and monopole distinct from its original linear polarization (LP). By embedding a slit on the ground plane, this antenna achieves a broad impedance bandwidth and circular polarization (CP). Measurements demonstrate a 10 dB bandwidth of 92.7 percent from 3.3 to 9 GHz and a 3 dB axial ratio (AR) bandwidth of 57.1 percent from 5 to 9 GHz, capable of covering the 5.725 to 5.85 GHz WLAN band. Meanwhile, LP is also obtained covering the 3.3 to 3.7 GHz WiMAX band. Compared with other recent work, wider axial ratio and impedance bandwidth, as well as a simpler, more compact structure are the key features.