The NeuroDisc

Book excerpt: Minimally-invasive tools for researching and treating neural disorders increasingly rely on high data rate, ultra-low-power wireless communication. This dissertation explores the use of backscatter communication to reduce the power consumption of wireless uplinks streaming high resolution neural telemetry. We present the development of the NeuroDisc, a custom wireless neural recorder leveraging a wireless backscatter uplink to obtain data rates of tens of megabits per second (Mbps) at orders of magnitude lower power consumption compared to commercially available alternatives, such as WiFi and Bluetooth. The design, analysis, and experimental validation of three different modulation techniques for backscatter communication are reported: (1) a 25 Mbps, 12.4 pJ/bit differential quadrature phase-shift keying (DQPSK) backscatter uplink for high rate telemetry; (2) a 1.0 Mbps, 198 pJ/bit Bluetooth Low Energy-compatible single sideband (SSB) frequency-shift keying (FSK) uplink for compatibility with off-the-shelf Bluetooth devices such as smartphones and tablets; and (3) a 1.25 Mbps, 160 pJ/bit all-digital orthogonal frequency division multiplexing (OFDM) backscatter uplink with the potential to improve reliability in multipath environments. Using the 25 Mbps DQPSK backscatter uplink, we validate the end-to-end system through in vivo neural recordings from the primary motor cortex of an anesthetized pigtail macaque. In the context of wirelessly recording from non-human primates (NHP) using the NeuroDisc, we investigate the dense multipath interference exhibited in a standard metal NHP cage and propose a novel method using digitally-controlled mode stirring to improve the in situ reliability of low-power wireless communication. These developments advance the state-of-the-art in low power wireless communication and lay the ground work for future innovation in ultra-miniaturized, battery-free prosthetics for bioelectronic medicine.