Experimental Study of L-band and S-band SAR Signal Penetration into Soil and Hard Surface

Abstract. The penetration depth of Synthetic Aperture Radar (SAR) signals is a critical parameter for assessing subsurface characteristics and detecting concealed structures. Although numerous empirical and scattering models have been proposed to estimate signal penetration depth (SPD), there remains a lack of understanding of SPD in various settings. In this study, we deployed a ground-based SAR system equipped with L-band (1.5 GHz) and S-band (3.0 GHz) SAR sensors and a microwave anechoic chamber to carry out experimental studies of SPD in soil with different volumetric water content (VWCs) and in hard surfaces of varying thicknesses of gravel and asphalt. At an incidence angle of 40°, the laboratory measurements indicate that the L-band SPDs in homogeneous clay with VWC levels of 4% and 18% are approximately 45–50 cm and 30–35 cm. The L-band signal can penetrate asphalt up to 9 cm, gravel up to 5 cm, and a composited layer of 2 cm gravel and 7 cm asphalt. The S-band can penetrate loose and compacted clay of 20‒25 cm and 15‒20 cm, respectively. The SPD in silt loam was about 15‒20 cm.