How a smart antenna maps hidden objects close to us?

Imagine having to find objects placed very close to a sensor, almost in its ‘comfort zone’. This challenge, called near-field localization, is difficult with traditional antennas. Scientists and engineers have now created a system shaped like a symmetric ‘eagle’, using a sparse array of antennas to save costs. The real magic? It transforms complex signals into a virtual ‘star map’, simplifying calculations. Using a technique called fourth-order cumulant, the system creates a reference image as if the sources were far away. Then, with an algorithm as precise as spectral analysis, it first estimates two angles and finally the distance. Tests show this method is much more accurate than others, improving angular accuracy by 65% and distance accuracy by 61.7%. In summary, it allows ‘seeing’ and locating objects in confined spaces with unprecedented precision.

The innovative part of this work lies in the use of a symmetric geometric arrangement of antennas (symmetric enhanced nested array) combined with the analysis of fourth-order cumulants. While the physical antennas are few and arranged irregularly to reduce costs, this method creates a much denser and orderly virtual image (virtual aperture). This ‘virtual duplication’ allows the application of estimation algorithms usually used only for far-field sources, but adapted for the near-field. The optimal parameter configuration for antenna placement was mathematically analyzed to maximize this ‘virtual aperture’. The final phase, which estimates distance via a one-dimensional spectrum, is made possible by a ‘pairing’ procedure based on l1-singular value decomposition, which avoids association errors between angular and distance parameters.