Low Power Smartdust Receiver with Novel Applications and Improvements of an RF Power Harvesting Circuit

Title of Document: LOW POWER SMARTDUST RECEIVER WITH NOVEL APPLICATIONS AND IMPROVEMENTS OF AN RF POWER HARVESTING CIRCUIT. THOMAS STEVEN SALTER JR., DOCTORATE OF PHILOSOPHY, 2009 Directed By: Professor Neil Goldsman, Department of Electrical and Computer Engineering, University of Maryland Smartdust is the evolution of wireless sensor networks to cubic centi meter dimensions or less. Smartdust systems have advantages in cost, flexi bility, and rapid deployment that make them ideal for many military, medical, a nd industrial applications. This work addresses the limitations of prior works of r esearch to provide sufficient lifetime and performance for Smartdust sensor net works through the design, fabrication and testing of a novel low power receiver fo r use in a Smartdust transceiver. Through the novel optimization of a multi-st age LNA design and novel application of a power matched Villard voltage doubler circuit , a 1.0 V, 1.6 mW low power On-Off Key (OOK) receiver operating at 2.2 GHz i s fabricated using 0.13 um CMOS technology. To facilitate data transfer in adverse R F propagation environments (1/r 3 loss), the chip receives a 1 Mbps data signal with a sensitivity of 90 dBm while consuming just 1.6 nJ/bit. The receiver operates without t e addition of any external passives facilitating its application in Sma rtdust scale (cm) wireless sensor networks. This represents an order of magnitude decrease in pow er consumption over receiver designs of comparable sensitivity. In an effort to further extend the lifetime of the Smartdust tr ansceiver, RF power harvesting is explored as a power source. The small scale of Smartdust sensor networks poses unique challenges in the design of RF power scavenging systems. To meet these challenges, novel design improvements to an RF power scav nging circuit integrated directly onto CMOS are presented. These improvements include a reduction in the threshold voltage of diode connected MOSFET and sources f circuit parasitics that are unique to integrated circuits. Utilizing these improvements, the voltage necessary to drive Smartdust circuitry (1 V) with a gre te than 20% RF to DC conversion efficiency was generated from RF energy levels m asured in the environment (66 uW). This represents better than double the RF to DC conver si efficiency of the conventional power matched RF energy harvesting circuit. The circuit is integrated directly onto a 130 nm CMOS process with no external passives and measures only 300 um by 600 um, meeting the strict form factor requirement of Smartdust systems. BREAK. [delete in final draft] LOW POWER SMARTDUST RECEIVER WITH NOVEL APPLICATIONS AND IMPROVEMENTS OF AN RF POWER HARVESTING CIRCUIT.