Fun with RADAR

Say 'radar' and most people think of cops and a speed trap, FAA air traffic controllers following airplanes, or NASA engineers tracking rockets. But RAdio Detection And Ranging can be used for a lot of purposes including some that are simply fun. Especially when you can put a whole radar system on a 5mm x 5mm chip, like ViaSat managed to do.

If you stand in a canyon and yell, you'll hear an echo when the sound of your voice bounces off the side of the canyon and back to you. Like timing a thunderclap to judge the distance to a bolt of lightning, if you time the echo of your yell and know the speed of sound (roughly 1000 feet per second) you can estimate how far away the cliffs are and how close a thunderstorm is. Flash, one-thousand, two-thousand, three..,boom! Storm is about a half-mile away.

With radar, you essentially do the same thing except you use a radio signal instead of sound, and the signal propagates at almost the speed of light (about 11 inches per nanosecond). Send a pulse, listen carefully for a radio echo, and you can tell how far away something is by measuring how long it takes for the signal to go out and bounce back.

If you know the direction your antenna is pointing when you receive the signal you know where to look for the target. Compute the difference in position between two received signals and you can tell the direction your target is moving.  Measure the change in frequency of your radio signal, and you can determine the speed of the target with respect to your antenna, although a target with zero speed may be traveling at a constant distance in a circle around you.

ViaSat has put all the radar electronics on a 5mm by 5mm chip. Add a power supply and an antenna and you're in business. It's not quite that easy of course, but that's essentially all you need.

ViaSat's chip is available for military and commercial applications that are a lot more serious, such as perimeter security, traffic management, and altimeters. In such applications the product has to survive challenging environmental conditions, take up up as little space as possible, use a tiny amount of power, and require no tweaking after it's installed—and do all that at a reasonable cost.

ViaSat's radar-on-a-chip is the only self-contained frequency modulated continuous wave radar sensor on a single chip. What's more, it can be easily tailored to different applications using digital interface software to control frequency and bandwidth. Best of all, it works over a wide temperature range because it continuously self-calibrates.

With those capabilities, the chip can be used by the military to control vehicles in driverless convoys, provide UAV navigation in tight spaces, or watch for small boat intruders when ships are in port. Civilian applications include adaptive cruise control so you don't have to brake and resume when traffic slows down.

ViaSat doesn't sell their chips retail, but a similar sensor will set you back only about $10. You won't be able to track passing aircraft or bust speeding drivers, but you could create a backup obstacle detector for your car or an intruder alarm for your house.

Or, just for fun, you could build a theremin—one of those weird-sounding electronic musical instruments. They date back to the 1920s when people used an antenna and oscillator to produce spooky sounds. With radar on a chip, you could do the same to measure the motion of your hands.

Radar isn't just about business and war, it can be fun too.


Unknown said…
Interesting post and the video.
William said…
Pretty cool stuff! I have enjoyed my iPhone immensely, and got my toe into the Apple culture. And I have realize that Steve Jobs is considered a genius by many and the Apple community. I don't believe he was really innovative a lot but he was a genius in integrating existing technology into new products. Such as the smart phone. Heck the GUI interface for computers, as first used in the Macintosh, came from the Xerox PARC center in Palo Alto invented in 1969. Here we have this little 5 mm x 5 mm radar chip. I think Diamler Benz was the first to integrate this forward-looking radar into cruise control. But think of the applications as yet on invented that this will be used in.

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