Non-reciprocal retro-reflective array for enhanced standoff on-metal target tracking and identification

The detection and tracking of targets in highly cluttered environments often poses a difficult engineering challenge as the strong clutter backscatter contained in the scene makes it difficult to distinguish the target of interest. A design concept based on a planar retro-reflective array tag to aide in the standoff detection and tracking of large metallic objects in a warehouse setting is presented. This retro-reflector design seeks to minimize the footprint of the tag by utilizing a contrast in the polarization properties of the target compared to the surrounding clutter. This allows for enhanced detection from a reduced size by maximizing the ratio of the target signal to that of the clutter. To accomplish this, a unique series fed dual polarized grounded coplanar waveguide (GCPW) patch antenna is designed and implemented with minimal cross-coupling among elements. The isolation among orthogonal polarizations of these elements allows for the integration of active devices into this design architecture to further reduce size, enhance detection and provide the array with unique non-reciprocal polarization properties in further contrast to those of the reciprocal clutter. This compact array is implemented at 26GHz. The design outline and measured performance both in a controlled and highly cluttered environment are presented.