Polarimetric Study of MMW Imaging Radars for Indoor Navigation and Mapping

In this communication, the application of sub-millimeter-wave imaging radars for collision avoidance and navigation of autonomous platforms in indoor environments is investigated. The polarimetric backscattering phenomenology of walls and doorways are studied to aid the design and system specifications of such radar systems. Polarimetric backscatter measurements of different wall covers, such as dry-wall, concrete blocks, wood, etc., as a function of incidence angle are carried out using a network analyzer operating at J-band. Also an instrumentation radar operating at 215 GHz is setup to collect backscatter data from corridors in an indoor setting. At each radar position, radar range profiles for both vertical and horizontal polarizations as a function of angle are used to form polar images for obstacle detection. It is shown that horizontally polarized incident wave can generate higher backscatter level and less reflection from smooth walls at steep angles of incidence and thus is the preferred polarization for this application. The polar images at each location are then co-registered in a global coordinate matrix to form a complete map of the interior layout. Feature extraction and image processing methods are then applied to remove multipath and enhance the radar map of building interiors.