GMK: Rethinking The Audio Jack

The lowly audio jack, taken for granted since the days of the transistor radio, is getting a lot of attention these days. Apple thought so little of it, in fact, that it eliminated it altogether with its iPhone 7, choosing to run analog signals through the power cable rather than keeping a separate audio jack. Now GMK, a fabless semiconductor startup in Korea, is taking the reverse approach—running power and digital communication through the audio jack.

Both are different takes on powerline communication, an idea that first surfaced about a century ago when electric power became widespread. Running power and communication through the same line is the reason that land-line telephones could continue working during a localized power failure. But powerline communication in the digital age has not seen widespread adoption because it is slow and not very energy efficient.

“The typical power line communication is 10 kilobits to 220 kilobits per second,” said Sean Ryu, chief operating officer at GMK. “We’ve increased the speed to 2 megabits per second.”

The advantage, according to Ryu, is that instead of passive earbuds connected to a smartphone, for example, this approach can provide noise cancellation without the need for a separate noise canceling headset. Unlike an audio jack, which is either on or off, this approach also allows audio communication to go into sleep mode and deep sleep mode.

“Today, a USB connection is the only possible option for data,” he said. “That adds a lot of cost because you’re dealing with many digital components, and it adds a lot of power. Our solution is very low power. We have developed our own modulation algorithm and designed a low-power way to communicate.”

GMK was started in April 2014 and has been working with Silicon Catalyst, an incubator based in Silicon Valley. The company initially is targeting smart phone manufacturers in Korea and China initially, using a 180nm UMC process, but it plans to expand from there to wearable electronics.

“Most of the information like body temperature and heartbeat are collected with a smart band or watch, but sometimes those devices don’t measure that very well,” said Ryu. “You can get correct information through an earphone. The same technology can be used in smart clothes, too. Today, there’s a sensor for power and data communication, but it requires four wires. With powerline, you have one cable for power and data, and the cable is smaller, which gives you more flexibility.”

James Hwang, GMK’s CEO, said the company’s secret sauce is in the algorithm for a high data rate. “It’s our own coding and decoding over a power line with a special signal,” he said. “Right now we have it running on a smartphone, but you can change the communication parameter.”

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