ImpSAR Technology
Technology Description
Eureka Aerospace is developing a "through-the-wall" imaging system capable of "seeing" through walls such as drywall, wooden wall, concrete wall and brick wall, using extremely high-resolution transient impulse Synthetic Aperture Radar (ImpSAR) system. The system is capable of remotely imaging targets such as man, weapons, file cabinets, tables etc on the "other" side of the wall, at large standoff distance.
The ImpSAR operates in a transient, impulse radar regime, where extremely short pulses (approximately 100 ps) having extremely large bandwidth (approximately 3.5 GHz) are radiated using a special impulse radiating antenna (IRA). The presence of the microwave energies in the 250-3500 MHz frequency range assures together with the very narrow pulsewidth, assures adequate penetration through walls and high resolution of microwave images (in the order of 5 cm in both range and cross-range directions).
The key specifications of the ImpSAR system are:
• Capability to image at standoff distance of at least 100 meters
• Exceptionally high spatial resolution of 5 cm in both range and
cross-range
• Quick acquisition time (fraction of a second)
• Capability to “see” through drywall, wooden wall, brick
wall, concrete wall
• Portable compact system
• System weight and size not to exceed 30 lbs and 4 cubic foot, respectively
• Day/night, all weather operations
• Host platforms include man, ground vehicle, helicopter and UAV
The tables below cite 1) ImpSAR features, advantages, and benefits and 2) ImpSAR comparison with other key competing technologies.
| Feature | Advantage | Benefit |
| Portable; lightweight and small size; relatively simple hardware implementation; extremely broad bandwidth centered at optimal wall penetration frequencies; off-the-shelf components; low-power microwave emissions | Can integrated in a variety of host platforms (UAV, Helicopter, Ground vehicle, Man); Exceptionally high resolution; penetrates essentially all types of walls | Reliable detection and identification of targets through-the-walls at large standoff distances; day/night, all-weather operations |
| Comparison | Ultrasound | Conventional radar |
Thermal (IR) | X-ray | ImpSAR |
| Resolution |
Good | Marginal | good | good | good |
| Day/night, all- weather | Yes | Yes | No | No | Yes |
| Wall penetration | Marginal | Good | Poor | Good | Good |
| Ground penetration | Yes | Yes | No | - | Yes |
| Capability to identify | No | No | Yes | No | Yes |
| Range achievable (m) (compact system) | 0.1 | 10 | 1 | 1 | 100 |
The weaknesses of the ImpSAR can be summarized as follows:
• Cannot operate through a completely metallic wall
• Regulatory issues-may interfere with public frequencies
• Requires motion of the platform
No interfacing equipment or facilities are needed for implementation of
ImpSAR technology.
Current State of Development
In April 2002, Eureka Aerospace conducted stationary Impulse radar tests at the Los Angeles Sheriff Department’s (LASD) Laser Village, as part of the SBIR Phase I effort, where “through-wall” radar signatures of specific targets were measured using Impulse radar. The tests produced a one-dimensional representation of the scattering by the test targets in the presence of the real dividing wall between the sensor and the targets. No imaging using synthetic aperture radar was planned nor executed during this Phase.
Figure
on the left presents a representative sample of the measured data during
Phase I effort in 2002. The shown signatures are the result of 2-way wave
propagation (Impulse radar-generated wave propagates through-the-wall, scatters
from the target on the other side of the wall, comes back through the same
wall and is received by the same radar). The test wall consisted of an 8-inch
concrete slab with two layers of 3-gage metallic rebar inside and yielded
28-dB two-way attenuation. The targets included Man, Man and M16 rifle,
M16 rifle only. Target signatures using Impulse radar are: Man with M16
(black), Man only (red) and M16 only (blue).
Moreover, limited tests carried out by Eureka during the Phase I effort, have demonstrated that the same system can easily penetrate the ground and can be used for detection of buried objects such as landmines, UXOs, underground bunkers and caves by generating a tomographic image of an underground strata.
During this SBIR Phase II effort, Eureka has built a 14-foot long Impulse SAR rail system capable of synthesizing the long aperture in the cross-range direction and thus generating high-resolution images. The system currently is undergoing full-scale testing at Eureka’s microwave facility. The test results will be available by the end of May 2005. While Phase II tests will be similar to those carried out in Phase I , using of prototype Impulse SAR enables the generation of a “photo-like” 2-dimensional microwave images.
Finally, Eureka Aerospace has developed all necessary analytical tools,
including processing algorithms and codes necessary for ImpSAR design, testing
and data processing. These include a novel “phaseles” interferometer
algorithm and computer code designed to generate 3-dimensional tomographic
images of the targets. Current Technology Readiness Level (TRL) is 6.
Experimental setup
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Prototype ImpSAR imaging through concrete wall with rebar
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Underground imaging
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Foliage penetration
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Recent Test Results
Please click links below to see recently acquired ImpSAR images in the following three application areas:
Through-the-Wall Imaging | Underground Imaging | Foliage Penetration