Public release date: 25-Jun-2012 [ | E-mail | Share ]

Contact: Matthew Chin mchin@support.ucla.edu 310-206-0680 University of California - Los Angeles

A team of UCLA researchers has created the most powerful high-performance nanoscale microwave oscillators in the world, a development that could lead to cheaper, more energy-efficient mobile communication devices that deliver much better signal quality.

Today's cell phones, WiFienabled tablets and other electronic gadgets all use microwave oscillators, tiny devices that generate the electrical signals used in communications. In a cell phone, for example, the transmitter and receiver circuits contain oscillators that produce radio-frequency signals, which are then converted by the phone's antenna into incoming and outgoing electromagnetic waves.

Current oscillators are silicon-based and use the charge of an electron to create microwaves. The UCLA-developed oscillators, however, utilize the spin of an electron, as in the case of magnetism, and carry several orders-of-magnitude advantages over the oscillators commonly in use today.

UCLA's electron spinbased oscillators grew out of research at the UCLA Henry Samueli School of Engineering and Applied Science sponsored by the Defense Advanced Research Projects Agency (DARPA). This research focused on STT-RAM, or spin-transfer torque magnetoresistive random access memory, which has great potential over other types of memory in terms of both speed and power efficiency.

"We realized that the layered nanoscale structures that make STT-RAM such a great candidate for memory could also be developed for microwave oscillators for communications," said principal investigator and research co-author Kang L. Wang, UCLA Engineering's Raytheon Professor of Electrical Engineering and director of the Western Institute for Nanoelectronics (WIN).

The structures, called spin-transfer nano-oscillators, or STNOs, are composed of two distinct magnetic layers. One layer has a fixed magnetic polar direction, while the other layer's magnetic direction can be manipulated to gyrate by passing an electric current through it. This allows the structure to produce very precise oscillating microwaves.

"Previously, there had been no demonstration of a spin-transfer oscillator with sufficiently high output power and simultaneously good signal quality, which are the two main metrics of an oscillator hence preventing practical applications," said co-author Pedram Khalili, project manager for the UCLADARPA research programs in STT-RAM and non-volatile logic. "We have realized both these requirements in a single structure."

The SNTO was tested to show a record-high output power of close to 1 micro-watt, with a record narrow signal linewidth of 25 megahertz. Output power refers to the strength of the signal, and 1 micro-watt is the desired level for STNOs to be practical for applications. Also, a narrow signal linewidth corresponds to a higher quality signal at a given frequency. This means less noise and interference, for a cleaner voice and video signal. It also means more users can be accommodated onto a given frequency band.

Original post:

UCLA-led research team develops world's most powerful nanoscale microwave oscillators