Wireless transfer between antenna arrays at the Talbot distance

Abstract

In modern multiple input multiple output (MIMO) wireless communication systems arrays of antennas are employed to enhance the data transfer rate. Scattering of the waves in the medium between the antennas can actually enhance the transfer capacity by decorrelating the available channels. Here it is shown that the transfer capacity between arrays of regularly spaced antennas depends intricately on the distance between the arrays and on the arrangement of scatterers. The relevant length scale is the Talbot distance $L_{\text{Talbot}}=2d^2∕\lambda$ known from optics as the distance where the self-imaging occurs of coherently illuminated gratings with $d$ the grating period and $\lambda$ the wavelength. The modulation of singular values of the channel transfer matrix occurs at fractions of $L_{\text{Talbot}}$.