Methods for Improving the Distance of Microwave Wireless Power Transmission With a Given Beam Collection Efficiency

Transmission distance of microwave wireless power transmission (MWPT) is a more important index than transmission efficiency and beam collection efficiency (BCE) in some specific applications, which should be analyzed and extended. To maximize the distance of MWPT, the model of MWPT between two planar antennas is built and formulated mathematically in this letter. Methods for improving the distance of MWPT between planar circular antennas with a given BCE are introduced. Optimal phase distribution for maximum transmission distance is derived based on functional analysis theory. Optimal amplitude distribution is obtained through numerical optimization. Numerical cases are calculated and compared to validate the methods. Finally, relationship between maximum transmission distance and aperture size is shown for approximate estimation.