Unified RF Rectifier-Demodulator for Energy Harvesting in Sub-GHz Wireless Implants

A unified RF rectifier-demodulator front end has been developed for wireless neural implants and other low-power wireless sensors operating in sub-GHz bands, including the 902-928MHz ISM band. The architecture integrates both blocks to enable efficient power harvesting and data demodulation, essential for neural stimulators, channel-selective neural recorders, and compact IoT or RFID nodes. Implemented in 180nm CMOS, the design employs a 4-stage fully differential cross-coupled differential-drive (CCDD) rectifier with a low-power DC demodulator supporting 1 MHz data rate. Including matching and packaging losses, a maximum power harvesting efficiency (PHE) of 32.2% is measured at 4-6dBm input, with efficiency above 20% for inputs over 0dBm. Although parasitic effects shifted the optimum frequency to 750MHz, functionality is preserved across 750-915MHz by tuning the off-chip matching network. These results demonstrate a compact, reconfigurable rectifier-demodulator front end suitable for energy-constrained neural interfaces and ISM-band IoT and RFID applications.