Coupling element antenna with slot tuning for handheld devices at LTE frequencies

Tunable antennas are a promising way to overcome bandwidth limitations for the new communication standards. Since it is the chassis that resonates in the low frequencies, its tuning is pertinent and allows for more compact size designs. This paper proposes a coupling element based antenna. A reconfigurable slot is inserted in the ground plane in order to lower its resonance frequency. The tuning is done by a capacitor across the slot. It is shown that covering all frequencies between the 900-GSM band and the 700-LTE band can be achieved. The radiating structure also presents a resonance in the high LTE band which is unaffected by the tuning mechanism of the lower band. Moreover, the efficiency can be optimized by an analysis of the currents across the slot. The study also shows that holding the device does not lead to additional mismatch losses which will further improve the overall efficiency.