Internal multiband loop antenna for GSM/DCS/PCS/UMTS operation in the small‐size mobile device

An internal multiband loop antenna suitable for application in the small‐size mobile device (groundplane length 50 mm only) is presented. Along the loop strip of the antenna, it is configured to have two symmetric meandered sections and a central widened section. With the configured loop strip, three resonant loop modes (0.5‐, 1.0‐, and 1.5‐wavelength loop modes) can be excited to form two wide operating bands centered at about 900 and 1900 MHz for GSM/DCS/PCS/UMTS operation in the small‐size mobile device. In addition, the loop antenna along with the short ground plane studied here shows near‐omnidirectional radiation patterns in the azimuthal plane for frequencies over the antenna's two wide operating bands, which is different from conventional internal mobile phone antennas and is advantageous for practical applications.