Techniques for miniaturization of circuits and systems for wireless sensing. Brian Otis Wireless Sensing Lab Seattle, WA, USA [email protected] Vision Existing technologies How do we get there? Circuit techniques Energy harvesting techniques Integration techniques.
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Techniques for miniaturization of circuits and systems for wireless sensing
Brian OtisWireless Sensing LabSeattle, WA, [email protected]
Critical challenges: miniaturization of - RF Link- Reference clock generation- Power sources
1.They are too large. Traditional architectures require multiple off-chip components, high die area, and a large quartz crystal resonator.
2.They consume too much power. Bluetooth & Zigbee (the “low power” standards) consume > 20mW. This eliminates the possibility of energy harvesting.
3. They require high-end processes and high transistor counts.
M. Usami et. al, ISSCC 2006
Frequency reference harvesting(100kHz clock)
M. Usami et. al, ISSCC 2006
Power dissipation >1W
Cost >$100 US
Provides two critical functions that are currently impossible to generate on-chip:
3. There is little energy available for sensing or computation.
4. They cannot form peer-to-peer networks.
Self-contained wireless sensing systems that can be fabricated exclusively with thin-film processing techniques.
This should include:
Peer-to-peer Wireless links
Electrical Sensor Interfaces
On-Chip Inductors (Q ~10)
Can we design an entire low-power radio link using MEMS resonators as a frequency reference?
Case Study: 2GHz transceiver for wireless sensors
Goal: Use matching RF MEMS resonators on the transmit and receive paths to define carrier frequency
Total Rx: 380uW
B. Otis et al., IEEE ISSCC 2005
Extracting energy from the environment to power the electronics reduces maintenance costs and increases capabilities
Bottom line: -Approximately 100uW/cm3 available(but efficiency decreases as volume shrinks)-Power consumption of electronics determines wireless sensor volume and capabilities
Large, stable temperature gradients often exist in ubiquitous sensing applications
Monolithic, solid state, possibleto integrate with circuitry
time(s)Proposed Idea: positive feedback ID generation
Su, Holleman, Otis, IEEE ISSCC 2007
1. Wireless sensor scaling is constrainedby energy source, antenna dimensions, and frequency reference
2. Self-contained wirelesssensors less than 1mm3 are on the horizon
3. Future chips will include circuitry, EM elements, MEMS structures, sensors, and power generation
4. Interdisciplinary collaboration is critical to focus our efforts on relevant sensing problems