Cutting Through the Radar Clutter

By Grace V. Jean

The same technology that allows fighter pilots to detect enemy planes in the skies may one day help ground troops peer around buildings in cities to track down insurgents.

At least, that is what scientists are hoping as they progress on research to make radar more effective in urban environments.
Radar detects objects by sending radio frequency waves out into an area. How long the signal takes to bounce off those objects and return to the emitting source indicates their speed and distance.

Such a system is effective in the skies, where there are few obstructions. But on the ground, and especially in the middle of a city, the signals encounter many obstacles that frustrate the process, says Edwin Chong, professor of electrical and computer engineering at Colorado State University.

In metropolitan areas, the signal can bounce off of multiple objects on the way to and from the intended target. For example, if radar is aimed at a moving vehicle, chances are that the signals would hit other cars, trees and buildings before reaching the vehicle. The signal would further disperse while returning to the source, which throws off the system’s ability to pinpoint the vehicle’s exact location.

Because of this “clutter,” radar is not commonly used in populated areas.

However, radar is an important sensing modality because it has some useful properties, such as the ability to see through smoke, says Chong, the principal investigator of a team of academic researchers who are working to improve the technology for the urban fight.

“The kind of technology that we’re continuing to develop aims to enhance our sensing capabilities in the urban setting and thereby enhance the ability of troops on the ground,” he says.

In a $1.6 million project funded by the Defense Advanced Research Projects Agency, Chong led scientists at Colorado State, Princeton University, Rensselaer Polytechnic Institute, Naval Postgraduate School and Melbourne University in designing signals that can provide more information about a detected object. They also improved the methodology in transmitting and processing those waveforms.

Traditional radar sends out only a single type of signal, or waveform. But with advances in electronics, radars can be built to transmit a variety of waveforms. Because waveforms bounce off of objects in unique ways, scientists have discovered how to harness those properties to give soldiers better information about their surroundings.

Chong compares the concept to one found in cellular wireless communications. To ensure that phone calls made to a certain number rings the correct person, cell phones must have the ability to discern and transmit different signals. The radar concept works in a similar way.

The researchers also have developed new algorithms to transmit those different waveforms in sequences. If one particular signal is generating good information about an object’s speed but not its location, the system may choose to send out another waveform to help determine the object’s location and verify the speed, explains Chong.

The Air Force Research Laboratory in Rome, N.Y., built a radar system to test the team’s processes, which improved the detection and tracking of a target tenfold.
Chong says his team is interested in pursuing the research further.

“It all depends on funding. There are a lot of things left to do,” he says. The scientists could continue working on the hardware side of the technology and begin networking the systems together. Or they could further develop the types of waveforms and the processing capabilities on the receiver end to attain high-resolution imaging.

Such research could yield a variety of new systems, such as small and inexpensive radar transmitters and receivers that could be deployed by the dozens. They could be mounted onto walls where they would communicate with each other via a wireless network to provide enhanced awareness.

“If we can get to a state where they can build these things like that, we would have achieved a lot. We’re not there yet,” says Chong.

Scientists envision their research enabling soldiers to see around the corners of buildings. The radar technology also has potential security applications on college campuses and airports, Chong points out. Those environments bear resemblance to the urban one with similar clutter challenges that can stymie traditional radar detection capabilities.

The team is looking for funding to continue its research.


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Topics: C4ISR, Sensors

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