A research group led by Professor Akira Matsuzawa and Associate Professor Kenichi Okada of Tokyo Institute of Technology has succeeded in developing a Bluetooth Low Energy (BLE) radio that operates with the world's lowest power by digitization.This is a result that does not require battery replacement for a long period of time and greatly accelerates the spread of IoT technology.
In recent years, BLE has been able to reduce power consumption by more than an order of magnitude compared to conventional Bluetooth, and its use has expanded explosively, especially in PC peripherals and smartphones, and it is expected to be installed in a wide variety of IoT terminals. There is.
The current BLE radio can be driven for about 2 to 5 years with a single button battery, but to eliminate the need for battery replacement during the useful life of the IoT terminal, it can be driven for 10 years or more with low power consumption. Was sought after.
The research group has significantly reduced the power consumption of BLE radios by letting the PLL circuit handle carrier playback and analog-to-digital conversion.The digital PLL circuit of the BLE radio developed this time has a new digital control delay circuit (DTC: a variable delay circuit whose delay time changes according to the digital control value), which has low jitter (fluctuation on the time axis of the signal) and a wide band. The characteristics have been realized, and it has become possible to use it with a BLE radio.
This halves the circuit scale required to receive conventional BLE radios and eliminates the need for an analog-to-digital converter (ADC).In addition, in order to improve the performance as an ADC, the resolution has been greatly improved by feeding back the offset amount.The power consumption of the BLE radio prototype made by the silicon CMOS process with the minimum wiring half pitch of 65 nm is 2.9 mW at the time of transmission and 2.3 mW at the time of reception, which is less than half that of the conventional BLE radio.
The newly developed BLE radio will be a stepping stone to the explosive spread of IoT devices by realizing maintenance-free operation.In addition, the patent-pending new DTC and the digital PLL using it can contribute to performance improvement and power consumption reduction by using it in a wide range of circuits other than radios.
