12.4 A 19μW 200Mb/s loT Tag Demonstrating High-Definition Video Streaming via a Digital-Switch-Based Reconfigurable 16-QAM Backscatter Communication Technique

Recent work in low-power backscatter modulation has enabled a new set of loT applications requiring low-to-medium throughput [1–4]. However, applications demanding medium-to-high throughput still rely on mW-level conventional wireless transceivers (TRXs). The needs of spectral-efficient high-throughput wireless communications at ultra-low-power still remain unaddressed. Pragmatic deployment of high-throughput, ultra-low-power backscattering is currently hindered by the difficulty of achieving high data rate and extreme structural simplicity at the same time: for the work in [1] (Fig. 12.4.1, upper left), by adjusting the parallel resistance formed by the I/Q transistors through programmable amplifiers (PGAs) as shown, up to 32-QAM is supported, however, gain adjustment requirement limits the max data rate to 2.5Mb/s; a digital-switch-based backscatter modulator was proposed in [2] and [3] (Fig. 12.4.1, middle left), but only QPSK is supported at max data rate of 2Mb/s; for the work in [4] (Fig. 12.4.1, lower left), higher data rate of 100Mb/s was reported, however, due to self-jammer issue caused by overlapping frequency of incident and reflected signals and the lossy power splitter, this data rate is only achievable when input power is greater than −5dBm (less than 25cm tag-to-AP distance with 23dBm EIRP), and for input power less than −30dBm (a more practical application scenario), only 0.256Mb/s was possible. Therefore, to date, practical ultra-low power backscatter IC that can achieve high-throughput with high spectral-efficiency (i.e., QAM) has not been demonstrated, exasperatingly, emerging loT applications, such as high-definition video streaming for wireless home monitor, require higher data rates than what current backscatter techniques can accommodate.