Remotely-operated non-contact rebar imaging in concrete using IR-UWB SAR and wavelet-based OMP clutter suppression

Accurate internal imaging of reinforced concrete (RC) structures is essential for safety assessment, particularly when construction details are unavailable. However, traditional ground-penetrating radar requires surface contact, limiting applicability in field conditions. This study presents a non-contact imaging system integrating impulse radio ultra-wideband (IR-UWB), Vivaldi antennas, and synthetic aperture radar (SAR) processing on a motorized scanning platform. To enhance image quality, wavelet-based clutter suppression using the Orthogonal Matching Pursuit (OMP) algorithm is applied before SAR reconstruction. This approach improves signal sparsity and effectively reduces clutter tailored to UWB characteristics. Experiments on a representative RC specimen with code-compliant cover thickness showed that the signal-to-clutter ratio (SCR) increased from 8.61 dB to 11.08 dB, and the image entropy decreased from 11.77 to 11.32, which enables clearer localization of closely spaced rebars. Although validated on a laboratory-scale specimen, the proposed SAR-OMP system demonstrates strong potential for practical, contactless, and high-resolution imaging in concrete inspection. • IR-UWB SAR scan system detects rebars embedded in concrete. • DSA-based SAR imaging improves rebar localization accuracy. • Wavelet-OMP filtering suppresses clutter and enhances signal clarity. • System is validated through tests on standard RC specimens. • The proposed system enables non-contact imaging of rebars via remote operation.