High Gain Monopole Antenna With Sleeve Ground Plane for WLAN Applications

In this letter, a compact monopole antenna is presented for wireless local area network (WLAN) applications. The proposed structure consists of a quarter-wavelength monopole, a ground plane, and an annular sleeve. The sleeve and the ground plane form a quarter-wavelength cavity. The open-ended cavity increases the radiation aperture and enhances the antenna gain. A small piece of substrate is used to support the monopole and match the input impedance. The simulated and measured results agree well. The measured impedance bandwidth is 160 MHz (2.38-2.54 GHz), which is sufficient for WLAN band. In the concerned band, the measured gain is above 3.6 dBi, which is 2.2 dB higher than that of a traditional monopole antenna.