Researchers Zap Microwave Interference

Nov. 18 -- Have you ever noticed how sometimes your kitchen microwave oven zaps more than last night's leftovers?

In some homes where wireless technology — cordless phones, Wi-Fi wireless computer networks, and cell phones — rule, the common kitchen appliance can be a noisy nuisance.

That's because microwave ovens emit high-energy radio waves that are roughly in the same or nearby frequencies used by those wireless systems.

Microwave oven makers traditionally try to mitigate the problem by adding internal shielding — basically, metal cages to trap microwave emissions that might cause interference.

But researchers at the University of Michigan in Ann Arbor may have stumbled upon a simple, more elegant solution.

Magnetically Managing Microwaves

Professor Ron Gilgenbach, along with professor Yue Ying Lau and graduate student Bogdan Neculaes, had been researching how to make better magnetrons — the devices that create microwave energy in ovens and, more importantly, radar systems.

With support from the U.S. Air Force Office of Scientific Research, the team had hoped their study would help create more efficient radar systems for the military.

"We were studying the noise of magnetrons which affects accuracy of radar [systems]," says Gilgenbach, a professor of nuclear energy and radiological sciences. "Any improvements would allow soldiers to detect smaller missiles and incoming weapons at greater distances."

And killing the "noise" — the random radio waves along the 2.4 gigahertz frequency — turned out to be a fairly simple trick, according to the work of Gilgenbach's team.

The Univ. of Michigan team discovered that by placing ordinary magnets in a specific pattern along the magnetron, they could sharpen or focus the microwaves into a single, exact frequency.