Miniaturized Low-Power and Energy-Efficient RF Wireless Communication and Sensing Systems

Abstract

This dissertation focuses on the miniaturized design and implementation of low-power energy-efficient wireless communication and radio frequency (RF) sensing systems, broadening the use case of smart home devices and Internet of Things (IoT). There are several challenges in miniaturizing wireless systems with an integrated antenna into a centimeter or even millimeter-scale. First, millimeter-sized antennae in RF are electrically-small, resulting in low radiation efficiency as well as difficulties to match the impedance. Second, the energy source is limited due to a small form factor battery. Third, bulky off-chip components, such as a high frequency crystal are unavailable due to reduced system dimension and low power consumption. In this dissertation, these challenges are analyzed and tackled by proposing new circuit architecture and system design techniques as well as new algorithms. Three prototypes of the proposed systems were implemented for evaluation and verification. The first one is a crystal-less 3x3x3 mm 915MHz asymmetric radio system optimized for non line-of-sight (NLOS) communication. The second work is a fully integrated 4x4x4 mm radio with newly proposed carrier frequency interlocking intermediate frequency (IF) transceiver architecture, enabling a symmetric sensor-to-sensor communication. Last, an energy-efficient and rapidly deployable RF localization system with crystal-less custom-designed tag was proposed together with a neural network time-of-flight estimation algorithm. The prototypes presented in this dissertation prove the feasibility of low-power and energy-efficient miniaturized designs to expand applications of wireless sensor nodes and improve the connectivity of devices in the IoT era.