Submicrowatt CMOS Rectifier for a Fully Passive Wake-Up Receiver

This work presents a wide-range, submicrowatt CMOS rectifier, which is designed to efficiently work at input power levels down to -31 dBm. The designed rectifier uses a novel threshold voltage compensation design, namely, the design of a custom-built single-stage rectifier that supplies a nanowatt current reference circuit. The generated bias current is mirrored to the core rectifier in order to precharge its CMOS diodes. The rectifier was optimized for a minimum number of gain stages while trying to minimize the overall input parasitic capacitance of the rectifier. The proposed CMOS rectifier was designed in an in-house 130-nm CMOS technology and includes a 1.6-kV human body level ESD protection at the input terminals. Measurements reveal a high 30% power conversion efficiency (PCE) over a wide input power range from -23 to -13 dBm for a 1- MΩ output load at 868 MHz. PCE of over 10% is achieved for a 1- MΩ load at an input power of -28 dBm. The enhanced startup at submicrowatt input power levels of the CMOS rectifier enables the design of an ultralow-power passive wake-up receiver. The measured sensitivity of -31 dBm for a 1-V output voltage across a capacitive load is the lowest reported in the literature so far.