An Ultra-Low Power 2.4 GHz Transmitter for Energy Harvested Wireless Sensor Nodes and Biomedical Devices

We present a 2.4GHz ultra-low power energyharvested narrowband transmitter (TX) for wireless sensing and biomedical devices. We used a 434 MHz RF energy for resonant cavity based wireless power transfer (WPT). An efficiency tracking loop maximizes the power transfer efficiency of WPT and achieves an efficiency of 11.5%. The TX comprises a voltagecontrolled power oscillator (VCPO) and a loop antenna which is patterned over a flexible Parylene C substrate to achieve biocompatibility. The loop antenna acts as a radiator as well as an inductive element for the VCPO, eliminating a power amplifier stage and bulky off-chip matching network. The TX is designed for low active and sleep mode power consumption to support both continuous-data mode or deeply duty cycled burst-data mode of transmission. Implemented in 0.18 mu m CMOS, the TX supports OOK and FSK modulations with the sleep mode power dissipation of 128 pW. Our active RF TX consumes an active-mode power of 70 mu W at 10 Mbps while radiating -33 dBm of power, resulting in an energy efficiency of 7 pJ/bit, which is the best reported till date.

Automated summary

The article presents a 2.4GHz ultra-low power energy-harvested narrowband transmitter for wireless sensing and biomedical devices. It features high power transfer efficiency and biocompatibility, supporting different data modes of transmission.