Enhanced FSK-modulated Ambient Backscatter Communication System

Development in ambient backscatter communications

“…This all‐digital solution, though having relatively low operation frequency, is more suited for legacy devices where no extra components can be retrospectively added. Apart from the above works, it has been demonstrated that 2FSK and CSS modulations can also be applied on ambient FM signals, achieving the longest FM BackCom link distance reported so far, up to 107 m for 2FSK FM BackCom in [52] and 130 m for CSS FM BackCom in [15]. This type of FM BackCom system block is presented in Figure 5.…”

“…This was achieved by introducing an Intermediate Frequency stage, which was controlled by real-valued transistor bias. In the same F I G U R E 2FSK or chirp spread spectrum (CSS)-modulated FM backscatter [15,52].…”

“…Borrowed and adapted from quadrature demodulation, it becomes possible to largely separate backscatter signals from ambient signals in frequency domain. This pre‐processing stage at backscatter receiver spreads the energy of ambient signals in wider bandwidth, becoming part of the noise floor, and it makes the backscatter tones clearly visible; see the experimental validation in Figure 6, as well as the field test video in [53]. It is worth pointing out that this promising approach has the potential to be applied to a diverse of ambient signals other than FM.…”

“… Measured 2FSK spectrum on ambient FM signals after proposed pre‐processing at the backscatter receiver [52]. Two frequencies of 60 and 70 kHz were chosen for 2FSK modulation.…”