All-Digital Single Sideband (SSB) Bluetooth Low Energy (BLE) Backscatter with an Inductor-free, Digitally-Tuned Capacitance Modulator
We present a novel all-digital approach for generating single-sideband (SSB) backscatter communication uplinks, using an inductor-free, digitally-tuned capacitance modulator. An example Bluetooth Low Energy (BLE) compatible single-sideband backscatter implementation is described. The FPGA-based approach presented here consumes 35.5 mW, of which 34.8 mW (98.2%) is due to digital logic in the FPGA, and only 600 uW (1.8%) is consumed by the backscatter modulator. The measured sideband suppression ratio is 10.7 dB. Over-the-air tests demonstrate compatibility with a completely unmodified (neither hardware nor software modifications) iPad, iPhone, Samsung Android Smartphone, and an off-the-shelf BLE chipset from Nordic Semiconductor. This all-digital approach points the way toward future single-chip, inductor-free SSB BLE-compatible backscatter sensors and devices.