Pattern diversity versus polarization diversity in UMTS mobile phones

In this paper, we describe the design of a novel two-antenna UMTS mobile phone structure able to either radiate vertically or horizontally polarized electric fields in the azimuthal plane of the phone depending the relative phase of the input signals of each antenna. Then, we introduce a structure where the two UMTS PIFAs are positioned in the same manner, but are neutralized to enhance their port-to-port isolation. This last structure is able to radiate vertically-polarized electric fields in the azimuthal plane of the phone with two slightly different pointing directions depending which antenna is fed. Then, we compute the diversity metrics of those two prototypes in different ideal and realistic propagation environments. It is especially revealed that the polarization-diversity scheme is not necessary the best solution for optimum performance.