Resolution improvement techniques for microwave imaging in random media using small wideband adaptive arrays

In this work we review and extend the approach for radar imaging using small, wideband, adaptive arrays by using a ray-tracing algorithm to simulate non-homogeneous environments. This allows the rapid investigation of radar imaging in more realistic environments that might be encountered in practice. We have previously shown that such arrays can be effective for short range backscatter imaging and source localization in free space using experimental arrays of four elements at 1 GHz and 20% bandwidth as well as twelve elements operating from 2-3 GHz. These arrays have been constructed to test the proposed algorithms and have demonstrated good results. We review the spatial resampling technique for array focusing. We discuss Approximate Signal Subspace Projection (ASSP) to suppress clutter. This technique allows more control over the angular resolution and the background clutter level. We review the ray-tracing algorithm that is required to generate data for imaging. Computer simulations are shown to demonstrate the use of adaptive array imaging in several non-homogeneous environments. The motivations for this work are indoor personnel localization systems, automotive radar and radar imaging seekers.