  We study the joint transmit (Tx) power allocation and receive (Rx) power
splitting for simultaneous wireless information and power transfer (SWIPT).
Considering the practical scenario of nonlinear energy harvesting (EH), we
adopt the realistic nonlinear EH model for analysis. To address the critical
nonlinearity issue due to the saturation, we propose to use multiple EH
circuits in parallel. An important problem is to maximize the achievable rate
by jointly optimizing Tx power allocation and Rx power splitting, which is a
nonconvex problem. In this paper, we first derive the optimal solution for any
number of EH circuits. Then we study how the number of EH circuits required to
avoid the saturation should be determined. From the obtained results, we draw
useful and interesting insights into the SWIPT system with nonlinear EH.
Numerical results demonstrate that employing multiple EH circuits substantially
enhances the SWIPT performance with nonlinear EH.
