A 1 mm ×1 mm CGM System on Die Achieving 1.65-nA/mM In Vivo Resolution and 0–40-mM/L Detection Range With ΔΣ Backscatter Technique

Diabetes has become a leading cause of death and disability all over the world. Continuous glucose monitoring (CGM) based on wireless power transfer (WPT) and backscatter communication enables wireless real-time telemetry to control glycemic levels in a long term. However, conventional backscatter techniques in CGM systems converted the sensing current into a bit stream or a frequency signal to switch the antenna, leading to two drawbacks: 1) Large power-harvesting antennas are required to complement the power loss in data converting and antenna switching and 2) Both the resolution and detection range are limited even with a high-performance glucose sensor. In this work, we propose a $\Delta \Sigma $ backscatter technique to demonstrate a system on die (SoD) within a $1\times1$ -mm on-chip antenna. Implemented in the 65-nm CMOS process, the proposed SoD achieves a telemetry error less than 0.25% with little impact on WPT, as well as a wide detection range of 0–40 mM/L. In vivo experimental results show that the CGM SoD realizes a resolution of 1.65 nA/mM.