Synthetic aperture analysis of multipath propagation in the ultra-wideband communications channel

We discuss synthetic aperture techniques for radio imaging and direction-of-arrival (DoA) analysis in an indoor ultra-wideband (UWB) environment. A wavefront reconstruction technique is used for visual representation of time-evolutionary wave traversal, and optical diffraction theory is used to transform complex channel data from a rectilinear synthetic aperture into its angular spectrum. Using this analysis with measured channel data, the DoA properties of UWB propagation are investigated. It is demonstrated that the channel experiences strong angular clustering in general. Initial evidence of frequency selective scattering is also reported. The significance of these results for beam-forming, diversity and MIMO systems is highlighted.