Enhanced Detection of On-Metal Retro-Reflective Tags in Cluttered Environments Using a Polarimetric Technique

The detection and tracking of targets in highly cluttered environments poses a challenge due to the strong clutter backscatter present in the scene. A design concept based on a planar retro-reflective array to aide in the standoff detection and tracking of large metallic objects in a warehouse setting is presented. While traditional methods to achieve enhanced detection involve an increase in gain of the target, this retro-reflector design seeks to minimize the footprint of the tag by utilizing contrasting polarization properties of the target compared to the surrounding clutter. This allows enhanced detection from a reduced size by maximizing the ratio of target signal to that of the clutter. To accomplish this, a unique series-fed dual polarized antenna is designed and implemented with minimal cross-coupling among elements. The isolation allows for the integration of amplifiers with switchable gains into the design architecture to further reduce size, enhance detection and provide the array with unique polarization properties further contrasting those of the clutter. These retro-reflector tags are provided a unique identification by modulating their radar cross section in a prescribed manner. This compact array is implemented at 26 GHz and design details including measured performance for this cross-polarized retro-reflective tag are presented.