Ultra low power, high sensitivity secure wake-up receiver for the Internet of Things

Abstract

Internet of Things (IoT) is emerging as the technology of the future where an estimate of billions of devices around us will be connected to the internet. When all of these sensors and nodes get connected to the cloud, a huge portion of their energy is consumed by their wireless communication systems. However, most of the sensors and nodes have a highly constrained power budget or even operate using a batteryless energy-harvesting scheme. With tons of data being transmitted through the IoT nodes, the specifications dictate an ultra low power design with secure communication. An ultra low power wake-up receiver integrated circuit is designed which can wake any node up using Bluetooth-LE. A new system level design methodology is introduced to map the higher level specifications to circuit level requirements with optimized duty cycling. A low power architecture is presented utilizing a mixer-first architecture along with a low power free-running oscillator. The system is designed to be highly programmable in order to track the local oscillator frequency variations through a cascade of reconfigurable filters along the receiver chain. While the whole system is optimized to be duty cycled in a scheme suitable for receiving the Bluetooth LE advertising packets, the local oscillator is also duty-cycled within the short interval of active operation in a harmonic rejection scheme for a 33% further power reduction. A prototype wake-up receiver with BLE compliance was designed using 65nm CMOS technology. The receiver correlates to a 32-bit reconfigurable wake-up pattern at a -90 dBm sensitivity using the advertising packets only without an actual connection. The system operates from a 0.7 V supply and consumes a 1 [mu]iW at a latency of a couple of seconds through incorporating an optimized system level duty cycling and within-bit duty cycling schemes. The power consumption can be be further scaled down to 400 nW or less at a latency of ten seconds or greater making it suitable for low power and low datarate IoT transceivers.