Intuitively, it’s easy to understand how a new MIT-developed radio works. The human inner ear—the cochlea—uses a combination of a liquid-filled channel and hairs that respond to frequencies ranging from 100 Hz to 10,000 Hz, a 100-fold range. Now imagine an RF circuit that works the same way, allowing it to quickly detect multiple frequencies in the radio frequency spectrum. Such a circuit modeled on the inner ear would receive a wide range of frequencies and process them in parallel. It will be faster than human-designed RF spectrum analyzers and could operate at much lower power.
"The cochlea quickly gets the big picture of what's going on in the sound spectrum," said Rahul Sarpeshkar, associate professor of electrical engineering and computer Science at MIT. “The more I started to look at the ear, the more I realized it's like a super radio with 3,500 parallel channels."
In addition to its use for radio applications, the MIT work provides an analysis of why cochlear spectrum analysis is faster than any known spectrum-analysis algorithm. Thus, it sheds light on the mechanism of hearing as well.
"Somebody who works in radio would never think of this, and somebody who works in hearing would never think of it, but when you put the two together, each one provides insight into the other," Sarpeshkar said.
The RF "cochlea" is embedded on a 1.5mm-by-3mm silicon chip. It works as an analog spectrum analyzer, detecting any electromagnetic waves in its perception range. The electromagnetic waves travel through electronic inductors and capacitors, analogous to the biological cochlea’s fluid and membrane. Instead of hair cells, the RF cochlea uses transistors.
The analog RF "cochlea" chip consumes about 100 times less power that would be needed to digitize the entire bandwidth. It is also faster. This makes it ideal for use in “cognitive” radios, which must quickly find the optimum RF frequencies over a broad spectrum range to provide the most reliable communication without interfering with other radios.
The MIT News article "Drawing inspiration from nature to build a better radio" has additional information, links and pictures.
Read all of Doug Lung’s RF Report.
