You might think that a personal radar system is something you can safely live without. But makers of radically smaller and cheaper Walkman-size radar systems are betting you're wrong. The radar is about to show up in everything from burglar alarms to hand tools. It will measure the water level in toilet tanks and the oil level in car engines. It will warn drivers of blind spots and monitor the triggering of air bags in collisions.
Thomas E. McEwan, a researcher at Lawrence Livermore National Laboratory in Livermore, Calif., stumbled across the concept of personal radar while figuring out how to measure the output of miniature nuclear-fusion reactions created by the lab's Nova laser, the world's most powerful. The technique he devised to monitor the reactions could be used to make a radar receiver, he reasoned. So he put together $10 worth of components in a plastic box the size of a pack of cigarettes, and it worked.
McEwan's "micropower impulse radar" (MIR) sends out about 2 million pulses a second, each lasting at most a few billionths of a second. It works at ranges of 150 feet or less and can run for years on a single battery. It's not only cheap and small but uncannily accurate, capable of measuring distances as small as fractions of an inch. McEwan underestimated its potential at first. "I thought it would make a very cool burglar alarm," he says. "It was the only thing I thought of."
Industry had a few other ideas. In the past two years, more than 3,000 companies have looked into the technology, and 15 have paid $100,000 each to license it. McEwan has 30 patents pending or issued and will probably net about $300,000 as his share of the $1.5 million in royalties under the terms of Lawrence Livermore's patent agreement. (He won't confirm the figure.)
The first products are coming to market. Amerigon Inc. of Monrovia, Calif., has incorporated McEwan's radar into a sensor that helps drivers avoid backing into objects. The radar--with warning lights and an audible alarm that rises in pitch as you get closer--should be used in a half-dozen car models by next year, Amerigon says. The startup also is developing a complete auto safety system with AlliedSignal Inc. Among other uses, the radar could tell if a passenger is leaning forward in the seat. If so, the passenger's air bag would open slowly at first to ease the passenger back.
MINE DETECTOR. The most complex micropower systems have an array of radar modules. The arrays can distinguish images through concrete, under the ground, or behind walls. A small processor combines the data generated by the various modules into a single image (diagram). McEwan is working with the Defense Dept. on a mine detector and with the Transportation Dept. on a device to check for corrosion of metal reinforcements in concrete bridges.
Zircon Corp., of Campbell, Calif., which makes the popular Stud Sensor, is making a radar array to spot steel rods in concrete and pipes in walls. It is planning products that can find wires, pipes, and sewer lines underground. These tools should be more accurate and versatile than the original Stud Sensor, which detects studs inside walls by looking for variations in electrical capacitance. "We're going to give the everyday contractor access to tools that will eliminate a lot of guesswork and frustration," says President John R. Stauss.
MIR, like conventional radar, works by sending out a signal and listening for its echo. But instead of paying attention to every echo, it watches only for those coming from a certain distance away--say, 10 feet. The distance is adjustable. That was the key to making the system simpler and cheaper. Conventional radars must sift through and make sense of echoes and stray signals coming from all distances.
McEwan also came up with an ingenious way to detect the radar's pulses inexpensively. The system takes a series of "snapshots" of returning signals, each at the precise time an echo is expected back. The snapshots--actually measurements of voltage levels--are stored in a capacitor and then analyzed using cheaper, slower electronics during the lull between snapshots. It may be hard to believe there's much of a lull, with 2 million snapshots per second, but the pulses are so brief that it's proportional to one-second-long pulses separated by gaps of 15 minutes or so.
One early success has been level sensing, the surprisingly tricky business of gauging how much liquid or solid is in a tank. Tanks containing foam, vapor, or dust, as well as tanks with extreme pressures or temperatures, can easily foil even sophisticated sensors. Ultrasound, for example, can be fooled if signals bounce off of thermal layers in gasoline vapors or steam rather than off of the liquid surface. The radar sensor cuts right through to the liquid's surface.
Titan Technologies, which sells level controls for oil, gas, and chemical plants, has introduced an MIR sensor at a cost of $1,000, one-third the price of its mechanical float sensors and about one-tenth the price of level sensors using conventional radar. The price should come down further once the radar and the control circuits it requires are integrated onto a single chip, says John F. Grimes, vice-president at Titan, a Lampman (Sask.) subsidiary of Titan Pacific Resources Ltd. Says Grimes: "Over time, this radar should obsolete all of our products."
FLASH FLOODS. In the construction field, Cleveland's Pile Dynamics Inc. has built the radar into a system that records how much of a steel or concrete foundation pile remains to be driven into the ground. And for the environment, Remote Data Systems Inc. in Wilmington, N.C., in January introduced a battery-operated surface-water monitor for such uses as watching rivers and streams for flash-flooding or for ensuring that wastewater treatment pools don't overflow.
MIR will really hit the mass market when some company puts McEwan's design on a chip that sells for a dollar or so. McEwan thinks that may happen within a year. Zircon sees a through-the-wall radar priced at less than $50, and Amerigon hopes to sell a car back-up radar that could be installed for under $25. With prices like that, McEwan might find someone willing to build his burglar alarm--a self-adhesive plastic box to be sold on a hardware-store rack.