Daniel J. Yeager

Wirelessly-Charged UHF Tags for Sensor Data Collection

We present the WISP passive data logger (PDL), an RFID sensor data logging platform that relies on a new, wirelessly-charged power model. A PDL has no battery yet (unlike a passive sensor tag) is able to collect data while away from an RFID reader. A PDL senses and logs data using energy stored in a capacitor; the capacitor can be wirelessly recharged (unlike active tags), and data can be uploaded whenever the PDL is near a reader. Standard EPC generation 2 readers are used for WISP-PDL charging, ID-reading, and sensor data transfer. This allows WISP-PDLs to operate using commercial RFID readers as the only support infrastructure (for both data and power), and allows WISP-PDLs to co-exist with standard RFID tags. We describe the design and implementation of a prototype WISP-PDL, and report results from a short demonstration study that shows it can monitor the temperature and fullness of a milk carton as it is used over the course of a day.

A 9

Biosensors present exciting opportunities in novel medical and scientific applications. However, sensor tags presented to date cannot interface with practical sensors, lack addressability, and/or require a custom (high-cost) interrogator. Our tag provides these features via ultra-low-power circuitry including a low-noise biosignal amplifier, unique tag ID generator, calibration-free 3 MHz oscillator, and EPC C1 Gen2 protocol compatibility. In addition to design details and measurement data from the fabricated IC, we present in vivo muscle temperature measurement from an untethered in-flight hawkmoth.

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With continuous improvements in the ef?ciency of microelectronics, it is now possible to power a general-purpose microcontroller wirelessly at a reasonable range. Our implementation of RC5-32/18/16 on the WISP UHF RFID tag shows that conventional cryptography is no longer beyond the reach of a general-purpose UHF tag. In this paper, (1) we provide preliminary experimental data on how much computation is available on a TI MSP430F2132 microcontroller-based RFID tag containing approximately 8 KBytes of ?ash and 512 bytes of RAM, and (2) we show that symmetric cryptography is feasible on an RF-powered, general-purpose RFID tag — providing the ?rst implementation of conventional cryptography on an RF-powered UHF RFID tag as far as we are aware

A, Addressable Gen2 Sensor Tag for Biosignal Acquisition

A wirelessly powered 0.125 mm2 65 nm CMOS IC for Brain-Machine Interface applications integrates four 1.5 μW amplifiers (6.5 μVrms input-referred noise with 10 kHz bandwidth) with power conditioning and communication circuitry. The multi-node backscatter frequency locks to a wireless interrogator using a frequency-domain multiple access communication scheme. The full system, verified with wirelessly powered in vivo recordings, consumes 10.5 μW and operates at 1 mm range in air with 50 mW transmit power.

Maximalist Cryptography and Computation on the WISP UHF RFID Tag

The next generation internet will be the internet of things (and not just of computing devices like PCs, PDAs); this is presumed to be enabled by integrating simple computing plus communications capabilities into common objects of everyday use. Radio-frequency identification (RFID) is a compelling technology for creation of such pervasive sensor networks due to its potential for ubiquitous, low-cost/low-maintenance use. However, the current drivers for RFID deployment emphasize supply chain management using passive tags, implying that RFID sensor nets require advances beyond the components and system designs aimed at supply chain applications. This work provides a glimpse of how this may be achieved.

A Fully-Integrated, Miniaturized (0.125 mm²) 10.5 µW Wireless Neural Sensor

We present the NeuralWISP, a wireless neural interface operating from far-field radio-frequency RF energy. The NeuralWISP is compatible with commercial RF identification readers and operates at a range up to 1 m. It includes a custom low-noise, low-power amplifier integrated circuit for processing the neural signal and an analog spike detection circuit for reducing digital computational requirements and communications bandwidth. Our system monitors the neural signal and periodically transmits the spike density in a user-programmable time window. The entire system draws an average 20 muA from the harvested 1.8-V supply.

RFID: From Supply Chains to Sensor Nets

This paper presents a novel method for incorporating a capacitive touch interface into existing passive RFID tag architectures without additional parts or changes to the manufacturing process. Our approach employs the tags antenna as a dual function element in which the antenna simultaneously acts as both a low-frequency capacitive fringing electric field sensor and also as an RF antenna. To demonstrate the feasibility of our approach, we have prototyped a passive UHF tag with capacitive sensing capability integrated into the antenna port using the WISP tag. Finally, we describe how this technology can be used for touch interfaces as well as other applications with the addition of a LED for user feedback.

NeuralWISP: A Wirelessly Powered Neural Interface With 1-m Range

We demonstrate a simple RFID sensor network comprised of an Intel WISP and a commodity UHF RFID reader. WISPs are devices that gather their operating energy from RFID reader transmissions, in the manner of passive RFID tags, and further include sensors, e.g., accelerometers, and provide a very small-scale computing platform. We believe that the small form factor and lack of battery makes the WISP an attractive alternative to motes for many of the original smart dust applications that require very small or long-lived sensors. The Intel WISP that we demonstrate has an ultra-low-power microcontroller, 32K of program space, 8K of flash, and accelerometer and temperature sensors. It harvests power from and communicates sensor data to standard (EPC Class 1 Gen 2) UHF RFID readers with a range of roughly 10 feet. This combination of RFID technology and sensor networks raises many research challenges, such as how to function with intermittent power and how to modify RFID protocols to support sensor queries.

A capacitive touch interface for passive RFID tags

Passive RFID technology enables battery-free wearable and implantable sensors with an unlimited lifespan, small size, and sub-gram weight. These properties facilitate advanced biomedical research (such as untethered monitoring of freely-behaving insects and small animals) and unobtrusive human health monitoring. Passive sensor tags reported to date have employed simple ring oscillator temperature sensors with no protocol or addressability [1,2]. However, realistic applications demand accurate processing of µV-level biosignals and compatibility with industry standard RFID protocols.

RFID sensor networks with the Intel WISP

A 65 nm CMOS 4.78 mm 2 integrated neuromodulation SoC consumes 348 μA from an unregulated 1.2 V to 1.8 V supply while operating 64 acquisition channels with epoch compression at an average firing rate of 50 Hz and engaging two stimulators with a pulse width of 250 μs/phase, differential current of 150 μA, and a pulse frequency of 100 Hz. Compared to the state of the art, this represents the lowest area and power for the highest integration complexity achieved to date.