Compressed sensing is a signal processing paradigm enabling the acquisition and successful reconstruction of a sparse signal from a reduced set of measurements, potentially in violation of the Nyquist sampling criterion. In this paper the results of preliminary investigations into Compressed Sensing applied to the acquisition of wide bandwidth millimeterwave compact radar range data are presented. Primary motivations for application of Compressed Sensing to compact radar range acquisition and imaging include increasing data acquisition speed as well as reducing required data storage. In this work only signal reduction in the frequency domain is examined. Compressed Sensing fully-polarimetric compact range data acquisition and imaging for both a simple canonical target (cylinder) and a complex target (Slicy) are presented as radar cross section (RCS) measurements and interferometric inverse synthetic aperture radar (IFISAR) images. Correlations of compact range data provide a measure of error between the reconstructed and complete data sets as a function of target complexity and sub-sampling rate.
Three-dimensional radar imaging is becoming increasingly important in modern warfare systems, leading to an increased need for deeper understanding of the 3D scattering behavior. Fully polarimetric, three-dimensional radar signature data have been collected using 1/16th scale models of tactical targets in several indoor compact radar ranges, corresponding to radar data at X-band. The high-range-resolution data has been collected through a 2D aperture in azimuth and elevation. This data has been processed into 3D coordinates using a standard 3D Fourier transform. The radar signatures have also been rendered into 3D coordinates using Interferometric ISAR techniques. The results of applying compressed sensing techniques to the analysis will be presented. Mathematical 3D correlation analysis has been used to compare the results of each method of 3D reconstruction.
We present a prototype bistatic compact radar range operating at 160 GHz and capable of collecting fullypolarimetric radar cross-section and electromagnetic scattering measurements in a true far-field facility. The bistatic ISAR system incorporates two 90-inch focal length, 27-inch-diameter diamond-turned mirrors fed by 160 GHz transmit and receive horns to establish the compact range. The prototype radar range with its modest sized quiet zone serves as a precursor to a fully developed compact radar range incorporating a larger quiet zone capable of collecting X-band bistatic RCS data and 3D imagery using 1/16th scale objects. The millimeter-wave transmitter provides 20 GHz of swept bandwidth in the single linear (Horizontal/Vertical) polarization while the millimeter-wave receiver, that is sensitive to linear Horizontal and Vertical polarization, possesses a 7 dB noise figure. We present the design of the compact radar range and report on test results collected to validate the system’s performance.
In this study the polarization scattering matrices (PSM) of individual scatterers from a complex tactical ground target were measured as a function of look angle. Due to the potential value of PSMs in studies of automatic target recognition, a fully polarimetric, 3D spot scanning radar modeling system was developed at 1.56 THz to study the W- band scattering feature behavior from 1/16th scale models of targets. Scattering centers are isolated and coherently measured to determine the PSMs. Scatterers of varying complexity from a tactical target were measured and analyzed, including well-defined fundamental odd and even bounce scatterers that maintain the exact normalized PSM with varied look angle, scatterers with varying cross- and co-pol terms, and combination scatterers. Maps defining the behavior of the position and PSM activity over varying look angle are likely to be unique to each target and could possibly represent exploitable features for ATR.