Sine-Cosine Modulation for SSB Backscatter Radio Applications

The objective of this paper is to improve the efficiency and reliability of ambient backscatter. Specifically, this paper describes a novel tag-data modulation technique for backscattering 802.11-compliant interrogation signals. The technique is suitable for implementation in recently published Single Sideband (SSB) backscattering tag designs. The primary advantage is that the tag-data receiver need not be aware of the interrogating station's data. This allows the tag to use any available 802.11 signal to backscatter its data. We also describe the demodulation algorithm necessary to extract tag-data at the receiver. A limitation is that commercial 802.11 receivers cannot directly demodulate tag data. At the same time, custom hardware will not be necessary, either. Simple modification to process the pre-detection data at standard 802.11 receivers will suffice. Although this paper describes the novel tag-data modulation specifically for incident 802.11 signals, the technique is suitable for other ambient signals as well.