Impact of modulation schime on rectifier RF-DC efficiency and optimal signal control technique

This paper investigates the impact of the modulation scheme and input power on rectifier RF-DC power conversion efficiency for wireless power transfer system. As the reference, we use the same rectifier with continuous wave (CW) input signal. The paper introduces simulation and measurement results to clarify the impact of QPSK/ 16 QAM modulated input signals with various symbol rates and input powers on the efficiency. The efficiency exhibits three characteristics depending on the input power. The efficiency drastically degrades in the high input power region. On the other hand, rectifier efficiency is significantly enhanced in the lower input power region (basically start-up region). In the middle input power region, signal modulation slightly improves the efficiency. The paper also Indiates that the efficiency depends on the symbol rate of the input signal.