While active functions in modern RF signal processors - such as amplifiers and mixers - are typically electronic and realized in semiconductor technologies, say the researchers, they can potentially be made smaller and better as acoustic devices - i.e., devices that use sound waves instead of electrons to process radio signals.
"Acoustic wave devices are inherently compact because the wavelengths of sound at these frequencies are so small," says Sandia scientist Lisa Hackett. "Smaller than the diameter of human hair."
However, until now, without the benefit of modern nanofabrication technologies, say the scientists, using sound waves has been impossible for many of these RF components. The last such attempts - made in the '70s - performed too poorly to be useful. Boosting a signal by a factor of 100 with the old devices required 0.4 inch (1 centimeter) of space and 2,000 volts of electricity, while at the same time generating lots of heat, and requiring more than 500 milliwatts of power.
Sandia's acoustic, 276-megahertz amplifier, however, can boost signal strength by a factor of 100 while measuring only 0.008 inch (0.2 millimeter) and requiring only only 36 volts and 20 milliwatts - demonstrating the vast, largely untapped potential for making radios smaller through acoustics, say the scientists. To amplify 2-gigahertz frequencies, which carry much of modern cell phone traffic, the device would be even smaller - 0.00003 square inch (0.02 square millimeter) - a footprint that would comfortably fit inside a grain of table salt and is more than 10 times smaller than current state-of-the-art technologies.
The researchers say they also created the first acoustic circulator, another crucial radio component that separates transmitted and received signals. Together, say the scientists, the tiny parts represent an essentially uncharted path toward making all technologies that send and receive information with radio waves smaller and more sophisticated.
"We are the first to show that it's practical to make the functions that are