Near-Field Focusing Operators for Planar Multi-Static Microwave Imaging Using Back-Projection in the Spatial Domain

A team of researchers from the Technical University of Munich, led by Matthias M. Saurer, has published a significant advance in microwave imaging technology. Their paper, 'Near-Field Focusing Operators for Planar Multi-Static Microwave Imaging Using Back-Projection in the Spatial Domain,' introduces a new mathematical formalism that improves image reconstruction for scenarios where the object is close to the sensor array. Accepted for publication in IEEE, the work moves beyond traditional back-projection—which only compensates for signal phase delay—by deriving analytical integral expressions for focusing operators. These operators apply crucial magnitude correction factors, which are particularly vital for accurate imaging when the scattering object is near the aperture plane.

The technical breakthrough lies in treating the imaging process as a low-pass filter in the spatial domain, which effectively suppresses high-frequency noise and artifacts. The team validated their modified multi-static back-projection algorithms using both simulated data and real-world measurements, demonstrating superior image clarity and a significant reduction in reconstruction artifacts. This advancement has direct implications for improving the resolution and reliability of microwave imaging systems used in non-invasive medical diagnostics, through-the-wall surveillance, and industrial non-destructive testing, where precise near-field imaging is critical.