UC San Diego

Wireless communication circuits often dominate the power consumption of Internet of Things (IoT) devices such as small battery-powered commercial wearables or low-power-wide-area-network (LPWAN) environmental sensors for infrastructure. More specifically, a large fraction of this power comes from node-to-hub or node-to-node networking requirements, especially when such devices communicate with low-to-medium average throughput. To reduce this power, instead of duty-cycling the main receiver, employing an auxiliary wake-up receiver (WuRX) that monitors the RF spectrum for a pre-defined wake-up signature either continuously or in duty-cycle fashion has been proved to be an effective solution. In this thesis, WuRX designs targeting ultra-low-power and high sensitivity for different usage scenarios are investigated. First, a WuRX for emerging LPWAN applications targeting to be used with the always-on WuRX communication protocol is presented. This design explores architecture-level and circuit-level techniques to operate with near-zero power consumption while achieving high sensitivity. Moreover, an active and a passive envelope detector (ED) that employ pseudo-balun architectures are also proposed, which further improve sensitivity and enable operation at a higher frequency band. On the other hand, WuRXs for commercial applications targeting to be used primarily with the duty-cycled WuRX communication protocol while being compatible with well-established wireless standards are also presented. First, a Bluetooth Low Energy (BLE) WuRX achieves low power, high sensitivity, interference-resiliency, and standard-compatibility through a combination of communication and circuit techniques, including high-Q filtering by a bank of FBAR resonators and a frequency-hopped mixer-first RF front-end that responds to a 4-dimensional (4-D) wake-up signature. This work is then further enhanced to achieve higher sensitivity while maintaining comparable interference-resiliency and power without the off-chip FBAR filters for a fully integrated solution. More importantly, this enhanced design is the first dual-mode WuRX compatible with both BLE and Wi-Fi transmitters, thanks to a carefully architected frequency plan that supports BLE advertisement channel hopping or a proposed subcarrier-based within-channel Wi-Fi frequency hopping scheme. As a result, the presented WuRX designs could potentially help enable new wireless IoT applications, particularly those that have low-to-medium average throughput requirements.