Improving practical sensitivity of energy optimized wake-up receivers: proof of concept in 65nm CMOS

We present a high performance low-power digital base-band architecture, specially designed for an energy optimized duty-cycled wake-up receiver scheme. Based on a careful wake-up beacon design, a structured wake-up beacon detection technique leads to an architecture that compensates for the implementation loss of a low-power wake-up receiver front-end at low energy and area costs. Design parameters are selected by energy optimization and the architecture is easily scalable to support various network sizes. Fabricated in 65nm CMOS, the digital base-band consumes 0.9uW (V_DD=0.37V) in sub-threshold operation at 250kbps, with appropriate 97% wake-up beacon detection and 0.04% false alarm probabilities. The circuit is fully functional at a minimum V_DD of 0.23V at f_max=5kHz and 0.018uW power consumption. Based on these results we show that our digital base-band can be used as a companion to compensate for front-end implementation losses resulting from the limited wake-up receiver power budget at a negligible cost. This implies an improvement of the practical sensitivity of the wake-up receiver, compared to what is traditionally reported.Comment: Submitted to IEEE Sensors Journa

Ultra low power transceivers for wireless sensors and body area networks

A transceiver suitable for devices in wireless body area networks is presented. Stringent requirements are imposed by the high link loss between opposite sides of the body, about 85 dB in the 2.45 GHz ISM band. Despite this, minimum physical size and power consumption are required, and we target a transceiver with 1 mm2 chip area, 1 mW active power consumption, and data rate 250 kbit/s. The receiver is fully integrated., fabricated and measured in 65-nm CMOS, and size and power consumption are carefully considered at all levels of circuit and system design. The modulation is frequency shift keying, chosen because transmitters can be realized with high efficiency and low spurious emissions; a modulation index 2 creates a midchannel spectral notch. A direct-conversion receiver achieves minimum power consumption. A tailored demodulation structure makes the digital baseband compact and low power. The channel decoder has been implemented in both analog and digital domains to find the most power efficient solution. Antenna design and wave propagation are studied via simulations with phantoms. The 2.45 GHz ISM band was chosen as a good compromise between antenna size and link loss. An ultra-low power medium access scheme based on a duty-cycled wake-up receiver is designed