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A 0.13μm CMOS low power wake-up radio is presented. The wake-up radio operates with -41dBm sensitivity at 915MHz using OOK modulation with a data rate of 100kbps while consuming 98nW active power, 11pW sleep power, and has an energy efficiency of 0.98pJ/bit. The wake-up radio occupies 0.03mm 2 and uses two off-chip components (an inductor and a capacitor). All biasing and calibration for process variation and mismatch is included on-chip. The entire radio operates from a single 1.2V supply.Index Terms -Wakeup radio, low power radio, body area networks, wireless sensor networks.

A boost converter for thermoelectric energy harvesting in 130 nm CMOS achieves energy harvesting from a 10 mV input, which allows wearable body sensors to continue operation with low thermal gradients. The design uses a peak inductor current control scheme and duty cycled, offset compensated comparators to maintain high efficiency across a broad range of input and output voltages. The measured efficiency ranges from 53% at mV to a peak efficiency of 83% at mV. A cold-start circuit starts the operation of the boost converter from 220 mV, and an RF kick-start circuits starts it from 14.5 dBm at 915 MHz RF power.

Most systems require a voltage reference independent of variation of power supply, process, or temperature, and a bandgap voltage reference (BGR) often serves this purpose. For ultra-low power (ULP) systems, the BGR may constitute a significant component of standby power, and the system start-up voltage is often determined by the voltage, V in , at which the BGR becomes operational. Lowering V in can also allow an ULP system to continue operation longer as its battery or energy harvested input voltage decreases. The minimum V in for state-of-the-art BGRs is restricted by V EB +V DS [1], where V EB is the emitter-base voltage of a pnp transistor, and V DS is the drain-source saturation voltage of a MOS transistor. Recent work brings the V in voltage down to 700mV [2]. There is a need to reduce the standby power and V in of a BGR to increase the lifetime of ULP systems. This paper presents a BGR circuit with measured minimum operating V in of 500mV, reducing the V in of [2] by 1.4×. Further, the power consumption of the proposed circuit is 32nW, which is 1.6× lower than the non-duty cycled BGR reported in [2]. A 2×-charge pump based bandgap core, a switched-capacitor network (SCN), and a current controlled oscillator and clock doubler circuit enable a BGR with a temperature variation of 75ppm/°C and power supply rejection (PSR) of up to -52dB at DC.

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Abstract-Body sensor networks (BSN) are emerging cyberphysical systems that promise to improve quality of life through improved healthcare, augmented sensing and actuation for the disabled, independent living for the elderly, and reduced healthcare costs. However, the physical nature of BSNs introduces new challenges. The human body is a highly dynamic physical environment that creates constantly changing demands on sensing, actuation, and quality of service. Movement between indoor and outdoor environments and physical movements constantly change the wireless channel characteristics. These dynamic application contexts can also have a dramatic impact on data and resource prioritization. Thus, BSNs must simultaneously deal with rapid changes to both top-down application requirements and bottom-up resource availability. This is made all the more challenging by the wearable nature of BSN devices, which necessitates a vanishingly small size and, therefore, extremely limited hardware resources and power budget. Current research is being performed to develop new principles and techniques for adaptive operation in highly dynamic physical environments, using miniaturized, energy-constrained devices. This paper describes a holistic cross-layer approach that addresses all aspects of the system, from low-level hardware design to higher-level communication and data fusion algorithms, to top-level applications.

This paper presents a batteryless system-on-chip (SoC) that operates off energy harvested from indoor solar cells and/or thermoelectric generators (TEGs) on the body. Fabricated in a commercial 0.13 μW process, this SoC sensing platform consists of an integrated energy harvesting and power management unit (EH-PMU) with maximum power point tracking, multiple sensing modalities, programmable core and a low power microcontroller with several hardware accelerators to enable energy-efficient digital signal processing, ultra-low-power (ULP) asymmetric radios for wireless transmission, and a 100 nW wake-up radio. The EH-PMU achieves a peak end-to-end efficiency of 75% delivering power to a 100 μA load. In an example motion detection application, the SoC reads data from an accelerometer through SPI, processes it, and sends it over the radio. The SPI and digital processing consume only 2.27 μW, while the integrated radio consumes 4.18 μW when transmitting at 187.5 kbps for a total of 6.45 μW.