Using pulse width and waveform modulation to enhance power conversion efficiency under constraint of low input power

This paper presents a novel wireless power transmission (WPT) technique by using pulse width modulation (PWM) and pulse waveform modulation (PWFM). Instead of using continuous wave for WPT, we could enhance the output voltage (V_out) and power conversion efficiency (PCE) of RF-DC rectifier by adjusting duty cycles and waveforms. We could determine the optimal duty cycle and waveforms to achieve the best performance according to the current through the load. Therefore, the PCE can be improved under constraint of low input power for biomedical applications. The WPT system and biomedical WPT system were established to perform wireless biomedical experimental verification. From the measurement, the PCE applying to a LED load can be improved by more than 30% at input power of -6 dBm with PWM WPT, and the PCE can be improved by 2.5 times by using PWFM WPT for biomedical applications.