An 802.11b-WiFi Backscatter Modulator Featuring 30dB PSLR with All-Digital Gaussian Pulse Shaping

This paper presents a spectral- and energy-efficient backscatter tag that generates 802.11b-WiFi packets that can be directly decoded by WiFi access points (APs). This is accomplished by: 1) proposing a pulse-shaped, frequency-translating BPSK backscatter modulator utilizing an all-digital Gaussian filter; and 2) implementing a low-voltage phase-locked loop (LVPLL) and an on-chip WiFi Barker processor to transform an RF tone into directly decodable backscattering WiFi packets. The proposed pulse-shaped modulator achieves a peak sidelobe ratio (PSLR) of 30 dB, representing a 17 dB improvement over conventional BPSK backscatter modulators, and an error vector magnitude (EVM) of 13.2%–15.5% at 11 Mb/s, all while consuming 19 µW. Wireless over-the-air measurements demonstrate a worst-case TX-to-Tag-to-RX range (with equal TX-to-Tag and Tag-to-RX distances) of 40 m for the pulse-shaped 802.11b-WiFi uplink when excited by a 30 dBm EIRP tone generator.