Design considerations for ultra-low energy wireless microsensor nodes

This tutorial paper examines architectural and circuit design techniques for a microsensor node operating at power levels low enough to enable the use of an energy harvesting source. These requirements place demands on all levels of the design. We propose an architecture for achieving the required ultra-low energy operation and discuss the circuit techniques necessary to implement the system. Dedicated hardware implementations improve the efficiency for specific functionality, and modular partitioning permits fine-grained optimization and power-gating. We describe modeling and operating at the minimum energy point in the subthreshold region for digital circuits. We also examine approaches for improving the energy efficiency of analog components like the transmitter and the ADC. A microsensor node using the techniques we describe can function in an energy-harvesting scenario.