Wideband antenna with crescent heads for omnidirectional communications

This paper investigates a wideband omnidirectional antenna that possesses 124.7% of fractional bandwidth. The antenna's two crescent-shaped radiating patches and their ultrawideband matching structures are printed on two laminates that are crossly placed vertically over the ground plane. Simulation shows that the structure on a single laminate radiates an "8"-shaped pattern on the horizontal plane. The cross formation of the two printed laminates generates an omnidirectional radiation pattern by superimposing two "8"-shaped patterns perpendicularly. The proposed antenna is fabricated and measured for demonstration. The measured results agree well with the simulation, indicating the omnidirectional antenna works from 1.38 to 5.95 GHz with a return loss of -10 dB. Simulation and measurement also show the gain variation on the xoy plane is 2 dB in the band of interest, which is small if the ultrawide bandwidth is considered. The above features make the proposed antenna a promising candidate for applications in the digital cellular system (DCS1800), long-term evolution (LTE2300/2600), wireless local area network (WLAN2400), and IEEE 802.11p.