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Low-power RF chip mimics inner ear

Posted: 09 Jun 2009 ?? ?Print Version ?Bookmark and Share

Keywords:RF chip? Bluetooth? GPS? cochlea RF chip?

Massachusetts Institute of Technology (MIT) researchers claim to have developed a fast, low-power radio chip imitating the human inner ear, or cochlea.

The RF chipRF cochleais capable of picking up mobile phone, GPS, radio, Internet and Bluetooth signals and, the researchers suggest, could enable wireless devices to receive cellphone, wireless Internet, FM radio and other signals.

According to the engineers, the RF cochlea chip is faster than any human-designed RF spectrum analyzer and also operates at a lower power.

The MIT team was led by Rahul Sarpeshkar, associate professor of electrical engineering and computer science, and his graduate student, Soumyajit Mandal, who designed the chip to mimic the cochlea, which uses fluid mechanics, piezoelectrics and neural signal processing to convert sound waves into electrical signals that are sent to the brain.

"The cochlea quickly gets the big picture of what is going on in the sound spectrum," said Sarpeshkar. "The more I started to look at the ear, the more I realized it's like a super radio with 3,500 parallel channels."

The RF cochlea, embedded on a silicon chip measuring 1.5mm by 3mm, detects the composition of any electromagnetic waves within its perception range.

It's said to consume about 100x less power than that required for direct digitization of the entire bandwidth, the researchers say.

They suggest this makes it desirable as a component of a cognitive radio, which could receive a broad range of frequencies.

Sarpeshkar and his students describe the device in a paper to be published in the June issue of the IEEE Journal of Solid-State Circuits. They have also filed for a patent to incorporate the RF cochlea in a software radio architecture that is designed to efficiently process a broad spectrum of signals.

The paper notes that as sound waves enter the cochlea, they create mechanical waves in the cochlear membrane and the fluid of the inner ear, activating hair cells (cells that cause electrical signals to be sent to the brain).

The cochlea can perceive a 100-fold range of frequenciesin humans, from 100Hz 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.

This is not the first time Sarpeshkar has drawn on biology for inspiration in designing electronic devices. His MIT group previously developed an analogue speech-synthesis chip inspired by the human vocal tract and an analysis-by-synthesis technique based on the vocal tract. The chip's potential for speech recognition and voice identification has applications in portable devices and security applications.

He is also working on projects inspired by signal processing in cells, and has worked on hybrid analogue-digital signal processors inspired by neurons in the human brain.

"Humans have a long way to go before their architectures will successfully compete with those in nature, especially in situations where ultraenergy-efficient or ultralow-power operation are paramount," Sarpeshkar said.

Reference: Mandal, S.; Zhak, S. M.; Sarpeshkar, R. A Bio-Inspired Active Radio-Frequency Silicon Cochlea. IEEE Journal of Solid-State Circuits, 2009; 44 (6): 1814-1828 DOI.

- John Walko
EE Times Europe

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