Contents 1. Introduction
Wireless sensor nodes, as the basic units of Internet of Thing (IoT), have been widely researched these years. There are several important considerations for designing wireless sensor nodes. The first is power consumption. Lower power consumption means longer operation time, smaller battery volume and minimum size. For next-generation energy harvesting systems, the power consumption is even more critical, and must be in the nanowatt level due to uncertain power-harvesting source. A second design consideration is the voltage supply. Future wireless sensors are preferred to be designed as batteryless systems, such that VDD should be low enough to meet the energy harvesting specifications, such as a solar-cell or DC-DC boost converter.
