Tiny energy efficient digital receiver for Bluetooth 5 and beyond

March 09, 2017 // By Jean-Pierre Joosting
Imec and Holst Centre have developed a novel phase-tracking receiver bringing further power and cost reduction for the next generations of Bluetooth and IEEE802.15.4 radio chips.

The ultra-low power digital-style receiver is 3x smaller than the current state-of-the-art. It supports supply voltages as low as 0.85-V and consumes less than 1.6 mW peak. An innovative low power antenna impedance detection technique enhances radio performance, especially for wearables or implantable applications.

The ongoing evolution towards an intuitive IoT has created unprecedented opportunities in various application domains. However, the deployment of massive numbers of interconnected sensors requires ultra-low power operation to enable multi-year battery life.

Imec’s novel receiver concept features sub-1nJ/bit energy efficiency and low supply voltage operation at 0.85-V while maintaining similar RX sensitivity as best-in-class products. The receiver employs digital phase-tracking to directly translate the RF input to demodulated digital data. A digitally-controlled oscillator (DCO) is used instead of a power hungry phase locked loop (PLL). The receiver, implemented in 40nm CMOS, is only 0.3mm 2, which is at least 3x smaller compared to the state-of-the-art. Due to this small size it can be manufactured at strongly reduced cost.

Especially in wearable or implantable devices, the antenna impedance can dynamically change due to variations in a device’s position or surroundings. This can deteriorate the radio’s performance and degrade battery lifetime. Imec demonstrated a fully integrated, sub-mW impedance detection technique for ultra-low power radios, enabling tunable matching between the antenna and the radio front-end. This technique can be implemented in an adaptive radio front-end to further improve receiver sensitivity and transmitter efficiency in the presence of antenna impedance variations.

“This innovative receiver concept will not only serve the new Bluetooth 5 devices, but provides our industrial partners a long term competitive advantage for multiple new generations of Bluetooth and 802.15.4 radios, still to come.”, says Kathleen Philips, Program Director Perceptive Systems at imec/Holst Centre.