A 1.0-Mb/s 198-pJ/bit Bluetooth Low-Energy Compatible Single Sideband Backscatter Uplink for the NeuroDisc Brain–Computer Interface

Wireless brain-computer interfaces (BCIs) are highly energy constrained because of the need to minimize battery size and weight, as well as the need to minimize the thermal dissipation into the living tissue. We demonstrate an ultralow-power Bluetooth Low Energy (BLE) v5.0 compatible backscatter communication uplink for the NeuroDisc BCI. This backscatter approach is compatible with completely unmodified BLE devices such as PCs, smartphones, and tablets and has an energy consumption of under 200 pJ/bit, over 50× less than commercially available BLE transmitters. This article is the first to present an analysis and demonstration of single sideband (SSB) BLE backscatter, which increases the available channel power by +3 dB while suppressing out-of-channel emissions. An analytic model of SSB backscatter communication is provided, along with simulations showing how nonidealities in the achieved backscatter constellation impact opposite-sideband suppression. The experimental measurements of in-channel gain and opposite-sideband suppression are provided. Additional experiments demonstrate a range of 6 m using a +20-dBm external carrier source and an unmodified Nordic Semiconductor nRF51DK BLE adapter, while uplinking prerecorded neural data sampled at 500 Hz.