New fast radio chip mimics human ear

Cambridge, MA – Taking inspiration from the human ear, MIT engineers have built a fast, ultra-broadband, low-power radio chip that could enable wireless devices capable of receiving cellphone, internet, radio and television signals.

Rahul Sarpeshkar, associate professor of electrical engineering and computer science, and his graduate student, Soumyajit Mandal, designed the chip to mimic the inner ear, or cochlea. “The more I started to look at the ear, the more I realized it’s like a super radio with 3,500 parallel channels,” said Sarpeshkar.

They have filed for a patent to incorporate the chip – dubbed the ‘RF cochlea’ – in a universal or software radio architecture designed to process a broad spectrum of signals including cellular phone, wireless internet and FM.
The chip is claimed to be faster than any radio-frequency spectrum analyzer and to require a hundred times less power than would be required for direct digitization of the entire bandwidth.

As sound waves enter the cochlea, they create mechanical waves in the cochlear membrane and the fluid of the inner ear, activating hair cells which cause electrical signals to be sent to the brain. The human cochlea can perceive frequencies from 100 to 10,000Hz. Sarpeshkar used the same design principles in the RF cochlea to create a device that can perceive signals at million-fold higher frequencies, which includes radio signals for most commercial wireless applications.

The RF cochlea, embedded on a silicon chip measuring 1.5mm by 3mm, works as an analog spectrum analyzer, detecting the composition of electromagnetic waves. These waves travel through electronic inductors and capacitors analogous to the biological cochlea’s fluid and membrane. Electronic transistors play the role of the cochlea’s hair cells.

The device demonstrates what can happen when researchers take inspiration from fields outside their own, says Sarpeshkar. “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,” he said.

Deatils will be published in the June issue of the IEEE Journal of Solid-State Circuits.