Efficiency improvement of an UWB rectifier by using optimized pulse modulation signal: simulation and experiments

This paper presents the contribution of RF pulse modulation signals on the efficiency improvement of an ultra-wide band (UWB) rectifier based on the voltage doubler topology. Simulations and measurements show that the RF-to-DC conversion efficiency is improved compared to CW (Continuous Wave) signal, especially on high loads. It has also shown, for the same average RF power value, that the optimum duty cycle to achieve maximum efficiency decreases as the load increases. Furthermore, the influence of the modulation frequency is lower. Indeed, when the modulation frequency varies, the maximum efficiency varies only slightly. For an output load of $ 99\text{k}\Omega$ and an RF power of -20dBm, a voltage gain of 8.5 dB, compared to a CW signal, is obtained by ADS simulation. This value is of 10dB in measurement. The results also show that the optimum output load moves from 3 $\text{k}\Omega$ for a CW signal to more than $ 20\text{k}\Omega$ for a pulse modulated signal. This allows making more convenient impedance matching when powering wireless sensors. Indeed, the power requirements of wireless sensors for IoT for example are constantly decreasing while their input impedance tends to increase.