Experiments of Time-Reversed Pulse Waves for Wireless Power Transmission in an Indoor Environment

A time reversal (TR) method is investigated for wireless power transmission in an indoor environment. Experiments performed with nanosecond pulses modulated at the frequency of 2.45 GHz reveal that the temporal and spatial focusing makes this technique valuable for applications of wireless power transmission. It is shown that the TR scheme avoids the fading phenomena that usually appear in an indoor environment when the power transmission is realized with a continuous wave: the voltage gain (respectively, the energy gain) can reach 30 dB (respectively, 20 dB) for the proposed scenarios. Moreover, it is theoretically proved that the TR technique is the optimal solution for an energy transmission, whatever the density of the multipath environment. In addition, simulations show that the voltage gain (respectively, the energy gain) of the TR technique is 3 dB (respectively, 9 dB) compared with the inverse filtering technique for a representative scenario. Other potential benefits of the method are discussed, notably concerning the power management of rectennas.