An experimental study is conducted on several retro-reflective beamforming schemes for wireless power transmission to multiple wireless power receivers (referred to herein as “targets”). The experimental results demonstrate that, when multiple targets broadcast continuous-wave pilot signals at respective frequencies, a retro-reflective wireless power transmitter is capable of generating multiple wireless power beams aiming at the respective targets as long as the multiple pilot signals are explicitly separated from one another by the wireless power transmitter. However, various practical complications are identified when the pilot signals of multiple targets are not appropriately differentiated from each other by the wireless power transmitter. Specifically, when multiple pilot signals are considered to be carried by the same frequency, the wireless power transmission performance becomes heavily dependent on the interaction among the pilot signals, which is highly undesirable in practice. In conclusion, it is essential for a retro-reflective wireless power transmitter to explicitly discriminate multiple targets’ pilot signals among each other.

• An experimental study is conducted on several retro-reflective beamforming schemes for wireless power transmission to multiple wireless power receivers.

• An experimental system of digital retro-reflective beamforming for wireless power transmission is constructed.

• Experimental results demonstrate that it is very necessary for a retro-reflective wireless power transmitter to discriminate the pilot signals of multiple wireless power receivers among each other.