A Digital Retro-reflective Beamforming System Based on FPGA for Wireless Power Transmission

An experimental system of digital retro-reflective beamforming based on FPGA for wireless power transmission is presented. The wireless power transmission experiments involve the following three steps. First, pilot signal is broadcasted by a wireless power receiver as "request for wireless power." Second, the pilot signals received by a wireless power transmitter are reversed in time. Third, the phase-conjugate signals are employed to construct a microwave power beam toward the location from which the pilot signal originates. To accomplish phase-conjugation, the pilot signals are downconverted to the baseband, then digitized and time-reversed by FPGA, and finally the time-reversed baseband signals are up-converted to the microwave frequency band. A least-absolute-value algorithm is implemented for time-reversal, which reduces the resource consumption of the FPGA. Experimental results demonstrate that the digital retro-reflective beamforming system is capable of constructing a wireless power beam toward the location of a mobile wireless power receiver in reaction to the pilot signal precisely.