Inverse Synthetic Aperture Radar Imaging with MATLAB Algorithms

The emerging ultrawide-band (UWB) impulse technology has found numerous applications in the commercial as well as the military sector. The rapid technological advances have made it possible to implement (cost-effective, short-range) impulse radar and impulse-radio communication and localization systems. Array beamforming and space-time processing techniques promise further advancement in the operational capabilities of impulse radar and impulse-radio communications to achieve long-range coverage, high capacity and interference-free quality of reception. We introduce a realistic signal model for UWB impulse waveforms and develop the principles of space-time array processing based on the signal model. A space-time resolution function (STRF), a space-frequency distribution function (SFDF) and a monopulse-tracking signal are derived for impulse waveforms received by a self-steering array beamforming system. The directivity peak-power pattern and energy pattern of the beamformer are also derived. Computer plots of the STRF, SFDF and the beam patterns are obtained. The directivity beam patterns of impulse waveforms are sidelobe-free and, therefore, there is no need for sidelobe suppression via amplitude weighting of the array elements. Also, the resolution angle for the beam patterns is derived as a decreasing function of array size and frequency bandwidth. Electronic beamsteering based on slope processing of monopulse waveforms is described.

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Principles of space-time array processing for ultrawide-band impulse radar and radio communications

In this paper, the application of ground penetrating radar (GPR) imaging for detecting the water leaks from buried pipes is examined. Experimental water leakage conditions for a shallowly buried plastic pipe are realized within the laboratory sand and outdoor soil mediums. The successive B-scan GPR measurements of the mediums are performed at various time instants while the water is leaking out of the pipe. The corresponding time-series B-scan images are reconstructed using the back-projection algorithm that we have specifically formulated for the subsurface GPR imaging applications. The signatures of the leak regions are then assessed by both direct interpretation of the resultant images and application of change detection procedures. The obtained results demonstrate the capability of GPR for locating the sources of the leaks accurately.

Ground penetrating radar imaging of water leaks from buried pipes based on back-projection method

A method of moments (MoM) analysis is developed for electromagnetic scattering from a dielectric body of revolution (BOR) embedded in a layered medium (the half-space problem constituting a special case). The layered-medium parameters can be lossy and dispersive, of interest for simulating soil. To make such an analysis tractable for the wide-band (short-pulse) applications of interest here, we have employed the method of complex images to evaluate the Sommerfeld integrals characteristic of the dyadic layered-medium Green's function. Example wide-band scattering results are presented, wherein fundamental wave phenomenology is elucidated. Of particular interest, we consider wide-band scattering from a model plastic mine, buried in soil, with the soil covered by a layer of snow.

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Wide-band electromagnetic scattering from a dielectric BOR buried in a layered lossy dispersive medium

In this paper, we consider the application of texture features for antitank landmine detection in ground- penetrating-radar data in the difficult scenario of very high clutter environments. In particular, we develop a technique for 3-D texture feature extraction, and we compare the results for landmine/clutter discrimination using classifiers that are built on 3-D as well as on 2-D texture feature sets. Our results indicate performance improvements across several different challenging testing scenarios when using the relevance-vector-machine classifiers that are trained on our 3-D feature sets as compared to the performance using the 2-D texture feature sets.

Texture Features for Antitank Landmine Detection Using Ground Penetrating Radar

A full-wave model is developed for electromagnetic scattering from buried and surface land mines (both conducting and plastic), taking rigorous account of the lossy, dispersive, and potentially layered properties of soil. The (polarimetric) theoretical results are confirmed via synthetic-aperture radar (SAR) measurements, performed using the US Army Research Laboratory's BoomSAR, with which fully polarimetric ultra-wide-band (50-1200 MHz) SAR imagery is produced. The SAR system is used to acquire a large database of imagery, including a significant distribution of naturally occurring clutter. Several techniques are used for mine detection with such data, including several detectors that are based on target features gleaned from the modeling, as well as a matched-filter-like detector that directly incorporates the target signatures themselves. In addition, the theoretical model is used to predict wave phenomenology in various environments (beyond the limited range of parameters that can be examined experimentally). Since the efficacy of radar-based subsurface sensing depends strongly on the soil properties, we perform a parametric study of the dependence of such on the target RCS, and on possible landmine resonances.

Ultra-wide-band synthetic-aperture radar for mine-field detection

Ground-penetrating radar (GPR) constitutes one of the oldest technologies for subsurface sensing. Most of such systems are placed in direct or near-direct contact with the earth surface. A significant drawback of this approach is the lack of "standoff", a particular problem for the detection of buried ordnance (e.g., mines). Moreover, it is time consuming to use such hand-held systems for large-area interrogation over variable terrain and foliage. The US Army Research Laboratory (ARL) has therefore undertaken the development of a synthetic aperture radar (SAR) system, with which significant standoff can be achieved. This system provides surveillance of large areas, the results from which can dictate the smaller regions over which conventional hand-held systems (e.g., electromagnetic induction, conventional GPR, and magnetometers) should be deployed. Therefore, while ideally we would like to use the SAR system to detect and distinguish each mine, we are particularly interested in mine field detection, over very large areas. Consequently, we need not detect each mine, but rather mine clusters. This simplified problem statement still constitutes a significant technological challenge, particularly in highly cluttered (natural and anthropic) environments.

Ultra-wideband synthetic aperture radar for mine field detection

A method and system for generating images from projection data; a preferred embodiment comprising inputting projection data from at least one receiving element; generating a first aperture or array of data points containing positional and signal data; arbitrarily and/or randomly removing data points from the first array to form a series of subarrays comprising different sets of data points; generating preliminary images from the subarrays; comparing the corresponding image pixels from two preliminary images to determine for each pixel location the lesser or equal pixel values; forming a merged image from the lesser or equal pixel values; and repeating the comparison of corresponding image pixels of another preliminary image to the merged image to determine the lesser or equal pixel values until a merged image of the desired quality is obtained. A preferred embodiment of the system may comprise at least one processor, comparator and/or image generator.

Method and system for forming an image with enhanced contrast and/or reduced noise

Self-calibrating an automatic, surveillance-based change detection system operating on noisy imagery comprises detecting a first image co-registered with a second image, wherein the first image and the second image each comprise pixels of a noisy image of a scene; detecting the second image co-registered with the first image, wherein co-registration of the first image with the second image comprises pixels from different images corresponding to a same location within the scene; producing a calibration factor based on the co-registered images; producing a modified ratio of pixel values corresponding to the first image and the second image from the same location within the scene; and comparing the modified ratio to a pre-determined threshold ratio value.

J. Sichina

Papers

Ultra-wide-band synthetic-aperture radar for mine-field detection

Ultra-wideband synthetic aperture radar for mine field detection

Method and system for forming an image with enhanced contrast and/or reduced noise

Metric and self-calibration for an automatic, surveillance-based change detection system operating on noisy imagery