Design of traditional and a novel space-efficient antenna-coupling elements for lower LTE/GSM mobile phones

The mobile phone antennas exhibit a very low real impedance value especially in lower LTE (698-787MHz) and GSM (824-960MHz) bands, since the antennas are electrically small compared to operating wavelengths at these bands. Obtaining sufficiently low reflection coefficient and high TRP in a considerable bandwidth from such an antenna is very challenging without exciting proper currents on the PCB of the device. So the main trend for mobile handset antennas has moved toward using an electrically-small coupler plate to excite those PCB currents. In this way, the input impedance of the coupling element-chassis combination has a relatively high real part and the quality factor of the system is now much more lower than traditional resonant antennas, enabling higher bandwidth potential with the help of a proper matching network. In this paper, this approach is followed to cover lower LTE (698787MHz) and GSM (824-960MHz) standards with a novel hollow coupling element antenna while keeping space available around and inside the antenna, for additional components or even another higher band antenna (DCS/PCS and UMTS).