The developments in mobile communication and broadcasting technologies have been remarkable. Developments in multi-functional planar antennas are especially desired for mobile communications. In this paper, single-feed planar antenna with three frequency bands printed on a dielectric substrate is proposed. Its resonance mechanism was clarified by analyzing the characteristics of return loss, radiation pattern, and current distribution on antenna elements using the FDTD (finite difference time domain) method. Moreover, two set-ups incorporating the three wireless systems were analyzed as an example of applications of the proposed antenna. One incorporated an 800 MHz cellular phone system, third generation cellular phone, and wireless LAN (IEEE802.11b). The return loss and radiation pattern characteristics were determined analytically and experimentally. The other incorporated digital terrestrial television broadcasting, a third generation cellular phone, and a wireless LAN (IEEE802.11b). Its characteristics were also determined analytically. These results showed that this antenna is useful as a multi-functional planar antenna in mobile communications.
