Future of Adaptive Circuits

1. Future of Adaptive Circuits Justin Kyungryun Kim Ph.D. Candidate, Electrical Eng. Stanford University justinkr@stanford.edu

2. Abstract • Ever increasing demands for lower cost and better functionality in communication devices are starting to drive analog circuitry to have adaptive features [1]. • Possibilities and promises of this new design direction have been explored. [1] A. Tasic, W.A. Serdijn, and J.R. Long, “Adaptive multi-standard circuits and systems for wireless communications,” IEEE Circuits and Systems Magazine, Page(s):  29 - 37

3. Outline • Introduction and Motivation • Adaptive Circuits • Finding a Niche • Adaptive Circuits to the Rescue • Real-Time Dynamic Range Control • Cognitive Radio • Ongoing Project • Reconfigurable ADC • Summary

4. Introduction and Motivation

5. Adaptive Circuits • Circuits that can trade off power consumption for performance on the fly. Reconfigurable Learning systems Self-tuning Self-optimizing Adaptive Electronics [Peter Asbeck]

6. Finding a Niche • Multi-Standard Communication Systems • Inefficiency in Worst-Case Design Methodology • Inefficient Spectrum Usage

7. Multi-Standard Communication Systems • Cell phone is a great example Video Audio Text Cell Phone Bluetooth Telephony LAN TV

8. Inefficiency in Worst-Case Design Worst case point Circuit is designed to operate even at worst-case situation which result in inefficient power usage at most of the time

9. Spectrum is a Commodity

10. Inefficiency in Spectrum Usage • Recent measurements by the FCC in the US show 70% of the allocated spectrum is not utilized [BWRC_White_Paper]

11. Adaptive Circuits to the Rescue

12. Niches and Solutions • Multi-Standard Communication Systems • Single circuitry designed to operate for multiple standards • Inefficiency in Worst-Case Design Methodology • Real-time dynamic range control • Inefficient Spectrum Usage • Cognitive radio

13. Real-Time Dynamic Range (DR) Control • Detect signal strength and control dynamic range of RF/analog circuitry Lower DR and power Higher DR and power

14. Cognitive Radio • FCC (Federal Communications Commission) “A cognitive radio (CR) is a radio that can change its transmitter parameters based on interaction with the environment in which it operates.” • Features of CR (A) Detect user need (B) Interact with the environment and figure out unused communication bands (C) Provide cheap communication solution Possible communication band

15. Ongoing Project

16. Reconfigurable ADC • Pipeline ADC with capability of adjusting speed and resolution with adaptive power • Main goal • Achieve ~state-of-the-art performance at every point on reconfiguration curve • Approximately 2x power reduction per bit of resolution dropped • Power approximately proportional to speed

17. K. Gulati and H.-S. Lee, "A Low-Power Reconfigurable Analog-to-Digital Converter," IEEE JSSC, Dec. 2001. Prior Art

18. The Simpler The Better • Analog becomes easier to turn on / off

19. Digitally Assisted Analog Design B. Murmann and B.E. Boser, "A 12-bit, 75MS/s Pipelined ADC Using Open-Loop Residue Amplification," IEEE JSSC, Dec. 2003.

20. Future Promises • Better functionalities and lower cost • Cheaper service with CR • Cellular service provider can lease their spectrum in secondary market to make more out of the spectrum they paid for • Wide area, reliable internet access • Low frequency TV signal has good propagation characteristics suitable for wide area internet access

21. Summary • Driving Force Towards Adaptive Circuits • Multi-standard communication systems • Worst-case design methodology in communication systems • Inefficient spectrum usage • Adaptive Circuits to the Rescue • Real-time dynamic range control • Cognitive radio • Reconfigurable ADC • Digitally assisted analog design concept can be effectively used to build a reconfigurable ADC