Advanced forward-looking radar

Better separation of components of the return signal leads to enhanced identification of objects containing electronic components such as IEDs


Defeating improvised explosive devices placed along roads has been of great interest to the U.S. military for over 15 years. Efforts have been made to adapt ground-penetrating radar for forward-looking, surface scanning. Innovative businesses can leverage and adapt the research for commercial applications.

Currently, forward-looking radar (FLR) on a mobile ground mounted platform can scan the route for force protection in an effort to detect targets of interest. The current FLR utilizes a high-frequency radio capable of transmitting a forward-directed beam over a frequency range. This frequency range may vary from one radar system to the next, but a typical radar scanning range would be from 300 megahertz to 1.5 gigahertz in 3 megahertz steps.

A Humvee approaches an object partially buried next to a road. In Iraq and Afghanistan, U.S. forces became suspicious of such objects, as they are sometimes improvised explosive devices. The Army Research Laboratory is developing technology to identify and characterize such objects from a distance using radar. (Army photo)

When the radar signal encounters an object, an echo is returned back at the fundamental frequency of the radar. The distance to the target can then be determined by either time of flight or by other means, such as frequency modulated continuous wave (FMCW), which measures the frequency difference between the transmitted and received echoes.

Existing FLR systems utilize the fundamental frequency of the radar transmitter to analyze the echo but natural objects, such as rocks, also produce an echo back to the radar system at the fundamental frequency of the radar transmitter. In order to differentiate between natural objects and military targets, common systems use complex algorithms in an attempt to image process the received echo. These algorithms, however, have not proven wholly reliable.

An Army researcher has invented a new FLR system overcoming the disadvantages mentioned above by leverage the knowledge that excitation of electronic equipment containing semiconductors, diodes, and other nonlinear devices generates harmonics of the fundamental frequency.

These harmonics form a part of the echo return to the FLR system. The Army system processes several harmonics of the fundamental frequency and the phase shift between the harmonics and the signal generated is compared and then tabulated over the various frequencies and their harmonics of the scanning frequency range.

A 4-D data cube containing these data points is then constructed and an algorithm separates the image represented by the harmonics. The imaging algorithm then displays the target on an interface. Since virtually all modern weapons contain electronic circuitry with electronic components, this radar system is able to differentiate military targets from natural objects.

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