Analysis of Modulation Techniques for SWIPT with Software Defined Radios

This work demonstrates the performance of software defined radios (SDRs) when transmitting multi-sine signals, which are already shown to increase RF to DC power conversion efficiency (PCE) at the receiver in a wireless power transfer system (WPT) [1]. In a system for simultaneous wireless information and power transfer (SWIPT) where the generated waveforms are modulated, however, we expect the transmitter efficiency to also be of great importance. Our goal is to evaluate the impacts on information transfer when transmitting QAM or PSK modulated power optimized waveforms (POWs) with two di↵erent SDRs. QAM and PSK modulated multi-sine waveforms are generated at fixed power levels while varying the amount of tones and modulation size and type. Error vector magnitude (EVM) is used as figure or merit for transmitter efficiency. The performed measurements show that generally, EVM decreases with increasing amount of tones. However, a high order QAM modulation of a high tone multisine signal at high power levels will increase EVM. Our work also shows that transmitter efficiency should not be neglected in SWIPT systems.status: publishe