Optimization of Microwave Wireless Power Transmission With Specific Absorption Rate Constraint for Human Safety

In this communication, we propose a new convex optimization algorithm for exciting the transmitting antennas of a microwave wireless power transmission (MPT) system that transfers maximum power under a specific absorption rate (SAR) constraint for human safety. The transformation of the initial NP-hard problem to a convex optimization problem is described in detail. We applied the proposed algorithm to several MPT scenarios with multiple transmitting antennas around and one receiver placed near a box-shaped phantom model. The channel response and the electric field response for the receiver and phantom required for the optimization process are obtained using full-wave electromagnetic simulations. The received power and the power transfer efficiency (PTE) of the proposed optimization (OPT) technique are compared with those of the time-reversal (TR) technique at 0.9 GHz. The results show that the OPT technique can transfer more power than the TR technique with a lower PTE within the SAR limit and that the proposed technique can be applied to various MPT scenarios.