MSA with Stacked Metal Rings for Rectenna System using Narrow Beam

When microwave wireless power transfer is performed using the narrow beam, a power reception distribution occurs in the plane of the power receiving array antenna, so that the RF/DC conversion efficiency of the entire antenna is degraded. Because the RF/DC conversion efficiency of the rectifier circuit has a peak characteristic, not only the output changes with the input power, but also the RF/DC conversion efficiency changes. Therefore, the antenna gain is adjusted to be the input power at which the RF/DC conversion efficiency is maximized for each block divided power receiving antennas. The RF/DC conversion efficiency of the entire power receiving antenna can be improved by making the power input to each block constant. Additionally, the design of the rectifier circuit can be configured with only one type. In this paper, in order to adjust the antenna gain, we propose a microstrip antenna (MSA) loaded with the stacked metal square rings for operating metal wall. It is cleared the calculated results that the antenna gain can be changed stepwise from 6.7 dBi to 10.1 dBi by changing the number of metal layers of MSA.