Introduction

Integrated circuits and systems are the backbone of modern information society, and play a vital role on enabling the internet-of-things (IoT), big data, autonomous vehicles, drones, and many emerging applications. For example, numerous wireless sensing devices are going to be deployed for environment or health monitoring. For such systems, the hardware consists of three major parts: communication, sensing, and power management. Due to the amount of transmitted/processed data and the number of devices are enormous, low-power and energy-efficiency have become crucial requirements for these devices.