Harmonic Elimination Strategy Design and USRP Implementation for FSK-based Backscatter Communication

Frequency shift keying (FSK) modulation can avoid the direct path interference problem in backscatter communication (BackCom). However, due to the limited number of reflection impedances of the tag, unwanted high-order harmonics are introduced, thereby degrading bit error rate (BER) performance. In this work, we investigate the harmonic elimination strategy for FSK-based BackCom. In particular, we first propose a novel multi-stage incident signal and the corresponding reflection strategy, which allows the tag to modulate the incident signal through absolute value operations, effectively suppressing harmonic generation. Then, we develop a USRP-based platform to experimentally verify the feasibility of our harmonic elimination strategy. Finally, the results show that our design can achieve a 12 dB attenuation in the third harmonic and up to 34 dB attenuation in high-order harmonics compared to conventional FSK-based BackCom without harmonic elimination, which consequently leads to improved BER performance.