Synthetic Aperture Radar 3-D Polarimetry

An synthetic aperture radar (SAR) 3-D polarimetry method using a radially polarized antenna is described. A 3-D target scattering model is developed based on a 3 x 3 polarimetric scattering matrix, allowing a target to be characterized by its interaction with 3-D electric field polarization vectors. The difficulties in measuring the 3 x 3 scattering matrix for a target are discussed, mainly that its measurement requires the target to be interrogated from multiple and specific incidence angles. The advantages of a radially polarized antenna for 3-D polarimetry are discussed, resulting from the diversity afforded in the polarization of the radiated electric field. An image reconstruction algorithm is then developed to enable 3-D polarimetry imaging to be performed from SAR measurements made with a radially polarized antenna, by which a 3 x 3 scattering matrix can be generated for every image voxel. Subsequently, a radially polarized antenna was fabricated and used to image two separate samples. The first target contained complex surface curvature and was used to demonstrate the efficacy of this technique for use on general targets. The second sample contained many small targets with different orientations (in 3-D) and was used to evaluate and demonstrate the accuracy of this method for performing 3-D orientation estimation.