Descriptor choice for UWB antenna arrays

The use of multiple antennas is an attractive option for ultrawideband communication and positioning systems. Despite intensive research interest, the framework for analysing ultrawideband arrays is ambiguous. For OFDM based systems which use many narrowband subcarriers, the preferred choice is the use of the classical array description by means of the array factor. For impulse radio systems, array factors cannot be used and new beam pattern descriptors have been developed. In this paper we explore and quantify the transition between narrowband and ultrawideband systems. We define the upper bandwidth for which it is still acceptable to use the description by the means of classical array factors. This limit enables a rule of thumb decision on the selection of a suitable UWB MIMO strategy