Quad-Band Circularly Polarized Antenna for 2.4/5.3/5.8-GHz WLAN and 3.5-GHz WiMAX Applications

A quad-band circularly polarized (CP) antenna for 2.4/5.3/5.8-GHz WLAN and 3.5-GHz WiMAX applications is proposed. Three CP modes operating at the 2.4/3.5/5.8-GHz frequency bands are first achieved by a patch antenna composed of an inverted-U-shaped radiator with additional I-shaped and L-shaped strips, all rotated by 45
$^\circ$
around the horizontal axis. By placing a simple frequency selective surface (FSS) of
$6 \times 6$
square metallic patches under this antenna, 5.3-GHz linearly polarized (LP) signals are converted into CP signals, producing a quad-band CP antenna. The measured
$-\hbox{10-dB}$
impedance bandwidth is 380 MHz (2.37–2.75 GHz) and 4.6 GHz (3.4–8 GHz). The measured 3-dB axial-ratio bandwidth reaches 5.4% (2.35–2.48 GHz), 8.3% (3.45–3.75 GHz), 3.7% (5.25–5.45 GHz), and 2.9% (5.7–5.87 GHz).