This chapter describes the wireless identification and sensing platform (WISP), a wireless, battery-free platform for sensing and computation that is powered and read by standards-compliant ultrahigh frequency Radio frequency identification device (RFID) reader. It focuses on a next generation of WISP that is smaller than its predecessors and uses a new demodulator called the "multifunction harvester–demodulator" that reduces demodulator current leakage thus yielding improved range. The chapter presents the WISP design and power budget, followed by experimental results on range, and several representative applications, including several sensors and the RC5 cryptographic algorithm. The WISP analog front end differs slightly in purpose from that of conventional RFID tags. Due to the relatively high power consumption of WISP, the rectifier is designed to supply more current than ordinary tags. To communicate sensor data from WISP to a computer through an RFID reader, the data must be encoded into the tag identification number.

A 65nm CMOS 4.78mm2 integrated neuromodulation SoC consumes 417μW from a 1.2V supply while operating 64 acquisition channels with epoch compression at an average firing rate of 50Hz and engaging two stimulators with a pulse width of 250μs/phase, differential current of 150μA, and a pulse frequency of 100Hz. Compared to the state of the art, this represents the lowest area and power for the highest integration complexity achieved to date.

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.

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

An architecture for generating a voltage reference at a fraction of the silicon bandgap is proposed. It uses a two-phase switched-capacitor network to add multiples and fractions of VBE and ΔVBE to achieve a near zero temperature coefficient without the use of resistors or op-amps. The 0.0055mm2 circuit, implemented entirely on-chip in 65nm CMOS, produces a voltage of 423mV, has a measured σ of 2.2%, and consumes 138nA while operating at a supply as low as 750mV at -35°C.

A wirelessly powered 0.125mm 2 65nm CMOS IC for BMI applications integrates four 1.5μW amplifiers (6.5μVrms input-referred noise for a 10kHz bandwidth) with power conditioning and communication circuitry. The multi-node backscatter FDMA communication scheme frequency locks to a wireless interrogator. The full system, verified wirelessly with MATLAB generated neural data, consumes 10.5μW, and operates at 1mm range in air with 50mW transmit power.

This work presents a 9.2 μA fully-passive sensor tag in 0.13 μm CMOS for biomedical research and human health monitoring. The sensor tag includes a 260 nA temperature-compensated 3 MHz reference oscillator. Subthreshold tag logic consumes 6μA from the 0.7 V supply. A 1.2 μA fully-differential chopper-stabilized amplifier with 1.25 μV rms input-referred noise is integrated for sensor interfacing. The system exhibits a range of 3 m and was deployed to perform wireless in-flight recording on a moth.

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.

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.

Passive RFID tags are becoming increasingly common in home and work environments. As RFID tags find new applications beyond shipment tracking, they are being embedded in objects throughout our environment. RFID tags are already being incorporated in credit cards for touch-free payments, in clothing for merchandise tracking, and in ID cards for building access control. All these “non-shipping” RFID tags are powered wirelessly and are capable of wireless communication and rudimentary computation. Thus they can be viewed as micro-computing platforms with wireless power and communication capabilities. While the functionality of today’s passive RFID tags is extremely limited, today’s tags can already be thought of as a layer of invisible computing that is seamlessly embedded in objects throughout the environment. This primitive layer of embedded intelligence could grow in sophistication if additional sensing and computation capabilities could be added to RFID tags. The authors’ goal is to evolve this layer of passively powered embedded intelligence by creating RFID tags that support sensors and can execute general purpose computer programs. This chapter reviews several years’ work on the development of our open, programmable passive RFID tag, the Wireless Identification and Sensing Platform (WISP). It also shows how to use the EPC Class 1 Generation 2 RFID protocol to implement advanced RFID sensing applications that go far beyond simple tag ID inventorying applications. Our first venture into sensor-enhanced RFID was the α-WISP shown in Figure 1 (Philipose et al., 2005). With this device, one bit of sensor data was encoded by using anti-parallel tilt switches to multiplex one of two RFID tag ICs to a single antenna. Thus, a reader could infer three states about a tagged item (tag right side up, upside down, or not present). This simple example of overloading the EPC ID to encode sensor data allowed inference of very coarse orientation information. However, the use of commercial RFID tag ICs restricted our ability to control the RFID communication channel and in turn our ability to configure WISPs for new applications.