Limits for low comlexity beam-steering for UWB antenna arrays

Low complexity beam-steering in UWB array systems uses a constant delay increment between adjacent antenna elements. Such a beam-steering is formally correct only for planar wave fronts in the far-field of the array. In the near-field the UWB signals received/transmitted by low complexity beam-steering do not perfectly overlap in the time domain. Therefore, the energy of received/transmitted signal is reduced. In this paper we use the previously published framework of beam patterns to quantify the reduction of received/transmitted signal energy in order to derive an approximate closed form expression for the minimum distance that is required to guarantee a permissible reduction of the energy of received/transmitted signal, which is application specific, even for low complexity beam-steering.