Penta-Band Printed Loop Antenna for Mobile Phone

It has recently been demonstrated that the loop antenna is very promising for achieving dual-band or multiband operation in the mobile phone. Although these loop antennas are mainly operated as half-wavelength and one-wavelength structures, unlike the conventional quarter-wavelength planar inverted-F antennas or low-profile monopole antennas for mobile phones, they still can be configured to occupy a compact volume inside the mobile phone for multiband operation. Such internal loop antennas for the mobile phone also show an attractive feature of performing as a balanced structure when it is operated at its one-wavelength resonant mode. In this case, the excited surface currents in the system ground plane of the mobile phone will be greatly suppressed. This property can lead to smaller antenna performance degradation when the mobile phone is held by the user´s hand and/or attached to the user´s head. In this paper, we present another promising printed loop antenna suitable for application in the mobile phone, especially for achieving penta-band operation.