Capacitively-Loaded Loop Antenna for Multi-Band Mobile Handsets

Due to the low profile and the simple structure, the planar monopole antennas and the planar inverted-F antennas (PIFA) have been very attractive in the mobile handset applications. Although the planar loop antennas possess similar features, they have not been discussed extensively. Moreover, the urging requirement for multi-band operations makes the handset antenna design more and more challenging. In this paper, we present a capacitively-loaded loop antenna with a low profile, simple structure, and multi-band capabilities. The operation principles are discussed. A prototype antenna is designed, fabricated, and tested. The impedance and radiation performances are shown to be satisfactory throughout the designed operating bands.