Tokyo Tech slashes power consumption in BLE transceiver

When transmitting, the transceiver consumes 2.9 milliwatts (mW) and when receiving, it consumes just 2.3 mW. Given that minimising power consumption is a requirement for the oncoming IoT era, these figures are remarkable, as they represent less than half the power consumed by previous transceivers.

Within the next decade, IoT is projected to become a multi-trillion US dollar industry. BLE is in the spotlight as a key technology spurring the growth of this fast-evolving market. Already embedded in millions of Apple and Android devices, BLE is the most used short-range wireless technology aimed at low-power and low-cost connectivity.

Low-energy solutions are in demand not only for smartphones and watches, but also for emerging applications in the medical and healthcare fields, factories and public infrastructure such as roads, bridges and tunnels. IoT sensors for early detection and warning systems could mean the difference between life and death.

"Our research grew out of this need for connectivity," explains Okada. "In an IoT world, trillions of devices will be used. To extend battery life and aim for maintenance-free operations, reducing power consumption is vital."

The BLE transceiver has excellent receiver sensitivity and high interference tolerance, while also realising the lowest power consumption. 

The transmitter employs an all-digital phase-locked loop (ADPLL), an attractive building block for BLE, as it is less susceptible to noise compared to its analog counterpart. The transceiver was designed in a 65-nanometer CMOS process.

In another study focusing on ADPLL, the researchers achieved a figure of merit (FoM)4 of -246 dB, one of the best obtained so far. The FoM is an important metric for evaluating the trade-off between performance and power consumption.

The above results arose from a project supported by Japan's New Energy and Industrial Technology Development Organisation (NEDO). In future, Okada says: "The PLL could operate on just 0.65 mW, and studies are underway to reduce our transceiver's power consumption even further."

The team will present their findings at the 2018 International Solid-State Circuits Conference (ISSCC). Held every February in San Francisco, the conference, popularly known as the Chip Olympics, is regarded as the leading forum on integrated circuit research and development.

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Image credit: Tokyo Institute of Technology.