Experiments on the element spacing in multi-antenna systems

Experimental results on the relation between the element spacing and the capacity inmulti-antenna systems are reported. In indoors, thecapacity is found to be almost independent on the element spacing, at least at a large distance to thetransmitter. Outdoors, the capacity is reduced at firstwhen the element spacing gets smaller. But when the spacing becomes smaller than half of the carrier wavelength, an increase of the capacity is observed which is not present without scattering. It is alsofound that the radiation characteristics of the elements increasingly differ from each other whenthe spacing gets so small. The capacity increase atvery small element spacing may therefore beattributed to mutual coupling effects increasing the diversity in the presence of scattering.