Modulation Techniques for Simultaneous Wireless Information and Power Transfer With an Integrated Rectifier–Receiver

Using the wireless signals to extend the sensors' battery life in a network or make them battery-free becomes prominent with the high number of sensors and circuits that are desired in the Internet of Things. Decreasing the power consumption of the sensors is also a valid point. Colocating information signals and power signals at the same frequency further decreases the size of the sensor and the used bandwidth. To fulfill all the mentioned requirements, we used an integrated rectifier-receiver (IRR) to decrease the power consumption and fully utilize all the received signals without splitting signals. We propose a novel magnitude ratio modulation, utilizing two-tone signals. We extend this paper by introducing the ratio phase modulation (PM) and, finally, merging the ratio amplitude-PM. The main advantage of the proposed modulations is the degree of freedom that it is possible to deliver a constant dc power to the sensor even with symbol variations, that is not possible by using M-ASK or ON-OFF keying modulations. If the channel is narrowband, the demodulation of our proposed modulation is possible even by not knowing the channel's attenuation. Since the IRR is highly nonlinear and this feature is used to fulfill our goals to receive power and information, we characterize the IRR's to show the symbol diagram considering the influence of nonlinearity of the circuit and its limitation on modulation. We report the power conversion efficiency to prove that the IRR is harvesting RF energy well with the proposed modulation.