A −76dBm 7.4nW wakeup radio with automatic offset compensation

Abstract

Event-driven sensor nodes have applications in agriculture, infrastructure, and perimeter monitoring and are characterized by spending the vast majority of their time in an asleep-yet-alert state. In this state, the node must wake to incoming RF wakeup commands from an antenna with minimal dc power, as the total percentage of power in sleep mode dominates if wakeup events are sufficiently infrequent. The RF wakeup receiver (WuRX) is one critical block of the node's asleep-yet-alert state. It must maximize sensitivity with power consumptions of 10nW or less to maximize battery lifetime or even enable battery-less systems that persist on energy harvesting [1-3]. These WuRXs must reliably detect wakeup signals as well as reject false wakeups caused by external interferer signals or noise. Otherwise, booting the full node into its active state when it is not needed can quickly relinquish power savings created by the wakeup radio in its asleep-yet-alert state.