Beamforming Optimization for MIMO Wireless Power Transfer With Nonlinear Energy Harvesting: RF Combining Versus DC Combining

In this article, we study the multiple-input and multiple-output (MIMO) wireless power transfer (WPT) system so as to enhance output DC of rectennas. To that end, revisit rectenna nonlinearity considering multiple receive antennas. Two combining schemes for rectennas at receiver, RF combinings, are modeled analyzed. For combining, optimize transmit beamforming, adaptive channel state information (CSI), maximize total power. compute a closed-form solution optimal beamforming. addition, propose practical circuit using phase shifter combiner also analog beamforming CSI. We analytically derive scaling laws function number Those confirm benefits antennas transmitter or receiver. They highlight significantly outperforms since it leverages more efficiently. types performance evaluations, based on nonlinear model realistic accurate simulations, provided. The evaluations demonstrate can be linearly increased by receiver relative gain versus in terms level is very significant, order 240% one-transmit antenna ten-receive setup.