Isolator-less near-field RFID reader for sub-cranial powering/data link of mm-sized implants

An efficient near-field RFID reader, delivering power to and receiving data from Brain-Machine Interface implants, is realized in 65 nm CMOS. A modified Class E/Fodd Power Amplifier with a current-sense resistor differentially drives a single segmented antenna, and acts simultaneously as TX and RX. It operates at 309 MHz and has 54% efficiency. The backscattered data is recovered from the current-sense resistor without the need for bulky RF isolators. The reader, as tested with a proprietary RFID tag through pig-skin and cow-bone, can deliver a maximum of 790uW to an implant through the skull while consuming 39.4 mW of power. It has a 2 Mb/s data rate with a BER of less than 1e-6.