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

Abstract

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 around the horizontal axis. By placing a simple frequency selective surface (FSS) of 6 x 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 -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).