Collaborative Research: Low Power CMOS Circuits and Systems for Next Generation Wireless Information Technology

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There is a rapidly growing trend toward embedding wireless capability into a wide variety of information technology products; recently in the form of single chip transceivers, and in the future perhaps integrated on-chip with the main product function. These devices must have low power consumption to satisfy battery conservation and thermal considerations. Good receiver sensitivity and signal handling are also essential in a crowded radio frequency (RF) spectrum; however, this requirement conflicts with low power circuit design. We propose to develop low power CMOS circuits that improve the trade-off between power consumption and RF performance. Current CMOS low noise amplifiers (LNA) have noise figures as low as 0.8 dB, input intercept points up to +18dBm, and power as low as 1.5 mW; however, these specifications cannot be obtained simultaneously. Likewise, CMOS mixers can meet demanding CDMA communications standards for linearity and noise figure, but only at high power cost.To address these problems we propose a number of strategies for (a) reducing power consumption for a given level of performance, and (b) allowing a dynamic trade-off of power versus RF performance. These trategies include: (1) reuse of amplifier stages at two different frequencies through reflex arrangements, thus reducing the number of high performance, high current stages required in receivers, (2) dynamically controlled positive feedback and bias in LNA stages, to allow power, signal handling, and noise figure to be traded off based on signal strength and interference, and (3) integration of charge pumps into individual drain supplies, to optimize the voltage for RF-critical stages while allowing the non-critical portions of a CMOS chip to operate at low voltage.Successful implementation will lead to improved range and life for wireless sensors, more reliable communications under adverse interference conditions, and ultimately to wider application of information technology in industry and science.