A new resonance phenomenon observed in UWB 14-50GHz SAR and its application to the retrieval of dielectric properties of scene features

Morrison, K. ORCID: https://orcid.org/0000-0002-8075-0316, Andre, D., Bennett, J., Finnis, M., Blacknell, D., Muff, D., Nottingham, M. and Stevenson, C. (2021) A new resonance phenomenon observed in UWB 14-50GHz SAR and its application to the retrieval of dielectric properties of scene features. IEEE Transactions on Aerospace and Electronic Systems, 57 (2). pp. 897-906. ISSN 0018-9251 doi: 10.1109/TAES.2020.3034030

Abstract/Summary

We describe the observation of a previously unreported resonance phenomenon in UWB SAR imaging, and its application in a novel scheme for the retrieval of dielectric properties of scene features. The resonance was observed in a 14-50GHz laboratory study of very high-resolution SAR imagery. It presented as a periodic fluctuation in the backscatter of a scene feature in response to changes in the radar measurement frequency. Complimentary static reflectivity measurements of a range of dielectric materials showed the phenomenon could be understood as a material behaving as a resonant microwave cavity. Modeling simulations were able to accurately reproduce the observed nulling characteristics for visually homogeneous materials (acrylic, MDF, plasterboard), and which dis-played a regular frequency spacing between nulls. Those with inhomogeneous structures (chipboard, plywood) showed much more irregular nulling patterns. The spacing of the backscatter nulls is set by the product of the permittivity and thickness of the material. By exploiting diversity in viewing geometry, the two terms can be separated and measured. The scheme offers a valuable new opportunity in SAR surveillance and monitoring of man-made structures