proposed antenna can operate in four different modes (higher frequency band LP, lower frequency band LP, LHCP, and RHCP) in the 2.4-GHz ISM band (2.4-2.485 GHz), which are obtained by switching the on-off states of two PIN diodes. The antenna satisfies the 10-dB return loss requirement in the 2.4-GHz ISM band. The antenna has a measured gain between 0.8 and 2.73 dBi over the operating bandwidth. Thus, the proposed antenna is a good candidate for WLAN and global positioning system communications. ACKNOWLEDGMENTS