A planar sleeve monopole antenna for bandwidth enhancement is proposed and experimentally studied. By embedding a concavity sleeve in the ground plane and etching two pairs of L-shaped slots on a printed circuit board, it is found that the operating bandwidth can be significantly enhanced and the impedance bandwidth could cover the GSM, DCS, PCS, ISM/Bluetooth (2400-2480 MHz), WLAN (2400-2484 MHz), and WiMAX (2500-2690 MHz) bands. By using a capacity load on the top of the antenna, the dimension of the antenna is reduced largely. The proposed antenna has good omnidirectional radiation characteristics and achieves gains to be 2.6, 3.2, and 3.5 dBi at 900, 1800, and 2450 MHz, respectively. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2235-2238, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25445