The following is from a NIST press release…….Dan

Researchers at the National Institute of Standards and Technology (NIST) have found theoretical evidence of a new way to generate the high-frequency waves used in modern communication devices such as cell phones. Their analysis, if supported by experimental evidence, could contribute to a new generation of wireless technology that would be more secure and resistant to interference than conventional devices.

The team’s findings point toward an oscillator that would harness the spin of electrons to generate microwaves—electromagnetic waves in the frequencies used by mobile devices. Electron spin is a fundamental property, in addition to basic electrical charge, that can be used in electronic circuits. The discovery adds another potential effect to the list of spin’s capabilities.

The team’s work—a novel variation on several types of previously proposed experimental oscillators—predicts that a special type of stationary wave called a “soliton” can be created in a layer of a multilayered magnetic sandwich. Solitons are shape-preserving waves that have been seen in a variety of media. (They first were observed in a boat canal in 1834 and now are used in optical fiber communications.) Creating the soliton requires that one of the sandwich layers be magnetized perpendicular to the plane of the sandwiched layers; then an electric current is forced through a small channel in the sandwich. Once the soliton is established, the magnetic orientation oscillates at more than a billion times a second.

“That’s the frequency of microwaves,” says NIST physicist Thomas Silva. “You might use this effect to create an oscillator in cell phones that would use less energy than those in use today. And the military could use them in secure communications as well. In theory, you could change the frequency of these devices quite rapidly, making the signals very hard for enemies to intercept or jam.”

Silva adds that the oscillator is predicted to be very stable—its frequency remaining constant even with variations in current—a distinct practical advantage, as it would reduce unwanted noise in the system. It also appears to create an output signal that would be both steady and strong.

The team’s prediction also has value for fundamental research.

“All we’ve done at this point is the mathematics, but the equations predict these effects will occur in devices that we think we can realize,” Silva says, pointing out that the research was inspired by materials that already exist. “We’d like to start looking for experimental evidence that these localized excitations occur, not least because solitons in other materials are hard to generate. If they occur in these devices as our predictions indicate, we might have found a relatively easy way to explore their properties.”

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M.A. Hoefer, T.J. Silva and M.W. Keller. Theory for a dissipative droplet soliton excited by a spin torque nanocontact. Physical Review B, 82, 054432 (2010), Aug. 30. 2010. DOI: 10.1103/PhysRevB.82.054432

Dave Jones’ latest EEVBlog episode is a graphical demonstration of why it’s important to get the polarity of electrolytics and tantalum capacitors right:

EEVBlog also has some interesting episodes on test equipment, microcontrollers, and product design. Check it out.

Back in the old days, the really good radios used mechanical filters. Now, according to this item, we could see a whole new type of mechanical filter, this time built with a microelectromechanical (MEMS) device.

Tiny ‘MEMS’ Devices to Filter, Amplify Electronic Signals
Purdue University News (08/10/09) Venere, Emil

Purdue University researchers are developing a new class of microelectromechanical (MEMS) devices called resonators that contain vibrating, hair-thin structures and could be used to filter electronic signals. Resonators vibrate in specific patterns, so they can cancel out signals that contain certain frequencies while allowing others to pass, making these devices useful for applications such as refining cell phone signals. The devices have led to a new type of band-pass filter, which is used in electronics to allow some signals to pass while blocking others, says Purdue professor Jeffrey Rhoads. This new class of resonators represents a potential way to further the miniaturization of band-pass filters while improving their performance and power efficiency. Incoming signals generate voltage that creates an electrostatic force, causing the MEMS filters to vibrate. In addition to their potential use as cell phone filters, resonators also could be used for advanced chemical and biological sensors for medical and homeland security applications, and possibly as a new type of mechanical memory element that uses vibration patterns to store data. “The potential computer-memory application is the most long term and challenging,” Rhoads says. He says the band-pass filter design promises to create better performance than previous MEMS technology because it more strictly defines which frequencies can pass and which are blocked.

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