Innovative Modulation Techniques for Integrated SWIPT Receivers
Despite mainstream simultaneous wireless information and power transfer (SWIPT) research focusing on time (TS) and power (PS) split receivers for SWIPT, integrated receivers allow for maximally reusing the WPT hardware for also information reception. Exploiting the WPT’s hardware’s rectifying behavior for energy harvesting and its similarity to envelope detectors for information reception allows for using WPT rectifiers for efficient power transfer while simply sampling the diode output to obtain information from the same waveform at the same time, with minimal power losses. This is because the diode’s non-linear behavior generates intermodulation products, which can be exploited for information transfer using WPT rectifiers as receivers. In addition to common modulation techniques designed for envelope detecting like single tone ASK or FSK, recent studies have found innovative modulation techniques that enable using multitone waveforms, which have shown to increase practical RF power transfer efficiency. SWIPT modulation techniques like biased ASK, PAPR modulation, tone ratio modulation and multitone FSK allow to expand classical information transfer techniques to further optimize of SWIPT performance. Additionally, it has been proven that complex modulation techniques designed for coherent information schemes, like OFDM, can even be received and decoded with a classical WPT rectifier when only a small modification to the signal is applied.