2019/05/19 by Ghanbari, Mohammad Meraj, Piech, David K., Shen, Konlin +6 · 2 citations
#Emerging Technologies (cs.ET) #FOS: Computer and information sciences #FOS: Electrical engineering #Signal Processing (eess.SP) #electronic engineering #information engineering
paper · doi:10.48550/arxiv.1905.09386
A 0.8 mm3 wireless, ultrasonically powered, free-floating neural recording implant is presented. The device is comprised only of a 0.25 mm2 recording IC and a single piezoceramic resonator that is used for both power harvesting and data transmission. Uplink data transmission is performed by analog amplitude modulation of the ultrasound echo. Using a 1.78 MHz main carrier, >35 kbps/mote equivalent uplink data rate is achieved. A technique to linearize the echo amplitude modulation is introduced, resulting in <1.2% static nonlinearity of the received signal over a ±10 mV input range. The IC dissipates 37.7 μW, while the neural recording front-end consumes 4 μW and achieves a noise floor of 5.3 μVrms in a 5 kHz bandwidth. This work improves sub-mm recording mote depth by >2.5x, resulting in the highest measured depth/volume ratio by ∼3x. Orthogonal subcarrier modulation enables simultaneous operation of multiple implants, using a single-element ultrasound external transducer. Dual-mote simultaneous power up and data transmission is demonstrated at a rate of 7 kS/s at the depth of 50 mm.