A wide-band cylindrical monopole antenna is presented. The antenna has a simple structure consisting of an upper hollow cylinder and a lower cone. When choosing the cylinder and the cone to be of equal lengths (10 mm in this study with the case of a 10-mm cylinder diameter), the antenna shows a wide operating bandwidth of about 8.8GHz (about 1.8 to 10.6GHz), making it easy to cover the UMTS (Universal Mobile Telecommunication System) band (1920

2170 MHz) and the 2.4/5.2/5.8GHz WLAN (Wireless Local Area Network) bands for mobile/WLAN dual-mode operation of a mobile phone.