Biased-FSK Modulation for Simultaneous Wireless Information and Power Transfer

This article introduces an innovative three-tone frequency-shift keying (FSK) modulation technique designed for application in simultaneous wireless information and power transfer (SWIPT) systems. The proposed method aims to improve the power conversion efficiency (PCE) through waveform design without adversely affecting the information transfer performance. Contrary to conventional FSK, which uses a uniform tone power, our method integrates a central tone with constant power and side tones with power proportional to the central tone. This Biased-FSK modulation scheme, combined with an adaptable information reception strategy, uses the frequency dependence of the rectifier’s transfer function to cater to low-and high-power scenarios, respectively. A mathematical model was developed for the PCE of the rectifier under this three-tone signal, highlighting the potential for improved PCE and reduced information distortion. The theoretical derivations are validated by empirical results, demonstrating the feasibility of this approach for enhancing the energy efficiency of SWIPT systems. The rectifier PCE achieved a peak of 62.84%. The use of Biased-FSK modulation enhanced the rectifier PCE by up to 9.04% and reduced the total harmonic distortion (THD) by 6.23% and the BER by a factor of 5.5.