A better signal

Engineers at

have developed a technique that could result in more accurate "ultra-wideband" radio signals for ground-penetrating radar, radio communications and imaging systems designed to see through walls.

The researchers first create laser pulses with specific "shapes," which precisely characterise the changing intensity of light from the beginning to end of each pulse. The pulses are then converted into electrical signals for various applications.

By controlling the shapes of laser pulses, the researchers are able to adjust the frequencies of the resulting radio signals and to produce signals with higher frequencies than are otherwise possible. Shorter signals make it easier to screen out interference and enhance image resolution, promising to improve the accuracy of systems used to detect landmines and other underground objects and for newly emerging devices that can look through walls and see what's on the other side.

"You want the best spatial resolution possible if you have two items buried close to one another," said Jason McKinney, a visiting assistant professor of electrical and computer engineering at Purdue. "If your pulse is too long, you get a combined reflection from both items back, but if your pulse is short enough, you get a separate reflection from each."