A Dual-Band Shared-Hardware 900 MHz 6.25 Mbps DQPSK and 2.4 GHz 1.0 Mbps Bluetooth Low Energy (BLE) Backscatter Uplink for Wireless Brain-Computer Interfaces

We present a dual-band, dual-mode shared hardware approach for backscatter based data uplinks. This all-digital approach yields a custom 900 MHz 6.25 Mbps differential quadrature phase-shift-keying (DQPSK) backscatter uplink and a 2.4 GHz 1.0 Mbps single sideband (SSB) BLE-compatible backscatter uplink from a single hardware device. The DQPSK mode achieves a per-bit modulator energy efficiency of 12.4 pJ/bit, while the SSB BLE backscatter mode achieves 198 pJ/bit, which is >50X lower than typical off-the-shelf BLE transmitters. The two modes are time-division multiplexed and share all the same hardware. Results from over-the-air testing are presented and confirm the successful reception of data streams from both modes using a custom full-duplex DQPSK receiver and unmodified Apple and Nordic Semiconductor BLE devices.