A 0.7 cm $^2$ , 3.5 GHz, $-$ 31 dBm Sensitivity Battery-Free 5G Energy-Harvester Backscatterer With 20 s Cold-Start Wake-Up Time for IoT-Enabled Warehouses

The rapid growth of the Internet of Things (IoT) demand ultralow power wireless systems. This article presents a 3.5 GHz Citizens Broadband Radio Service (CBRS) band wireless energy harvesting backscatter system, optimized for sensitivity and start-up time, making it ideal for fast inventory counts and extensive coverage in IoT-enabled warehouses. The system features a rectifier with $-$ 31 dBm sensitivity for 0.9 V output, enabling quick energy storage within $\sim$ 20 s from cold start. It employs backscattering blocks consuming 120 nW power with improved uplink data transfer resiliency to reduce minimize time. Incorporating a current-starved oscillator and self-clocked signal encoding, our design replaces low-dropout regulator (LDO) with a PTAT-current source inside backscattering/communication blocks to cut power consumption, while also boosting PVT-resiliency. Fabricated in TSMC 65 nm CMOS, the chip outperforms existing solutions in area and power efficiency. This comprehensive system not only boosts the capabilities of battery-free IoT tags but also opens new avenues for their application in industrial and commercial settings, paving the way for the next generation of IoT devices.