Abstract: A novel compact four-element antenna system for a clamshell phone is presented.It has a wide -10 dB impedance bandwidth from 1870 MHz to 2560 MHz,covering both UMTS and 2.4 GHz WLAN bands.The mutual coupling of the antenna elements is below -10 dB in the working bands.The parameter analysis is presented to discuss the effects of the key dimension parameters.The calculated correlation coefficients and mean effective gains(MEGs) indicate that it has good diversity performance.