SAR imaging using a coherent ultrawideband random noise radar

A coherent ultrawideband random noise radar system operating in the 1-2 GHz frequency range has been developed at the University of Nebraska. A unique signal processing procedure based upon heterodyne correlation techniques preserves phase coherence within the system, thereby enabling it to be used for synthetic aperture radar (SAR) imaging. The amplitude and the phase response of the system are used to form the frequency-domain target scattering profile matrix, which is then transformed into a SAR image. The ultrawide nature of the transmit waveform presents some unique challenges in signal processing. A technique has been developed that achieves the theoretical cross-range resolution, and this method has been validated by field measurements at 200 meters range to target. Controlled close-range SAR experiments at 8-10 meters range clearly demonstrate the ability of the system to provide high resolution images of targets located in a cluttered background and to extract the spatial geometry of the scattering center locations. The paper will present theoretical basis for random noise SAR imaging as well as experimental results and discussion.