Handset antenna performance using flexible MEBG structures

Smaller, lighter and more efficient cellular handsets are required by the market. Significant degradation of the handset antenna´s performance occurs due to interaction with the human body. Several mechanisms are responsible for this. Of major importance is the coupling of the user´s hand to the antenna. This coupling degrades the antenna performance in two ways, antenna detuning and efficiency degradation. The EBG property of periodic arrays suppresses surface waves that otherwise can propagate along a dielectric surface, such as the handset case. Miniature metallodielectric electromagnetic band gap (MEBG) arrays have been presented using closely-coupled arrays (Apostolopoulos, A.P.S.G. et al., IEEE Trans. Antennas and Propag.). We a propose flexible miniaturized MEBG structure embedded in the handset´s case as a means of improving the antenna performance in the presence of a human hand. The MEBG array is printed on a thin flexible substrate and is arranged conformal to the handset´s case. Imposing an EBG at the spatial location where the hand is typically holding the handset is shown to reduce the coupling to the antenna and hence the antenna degradation. Numerical and experimental results for a sample handset operating at 1.15 GHz are presented to demonstrate the validity of the proposed idea.