Transmitter optimization for mobile wireless power transfer (WPT) applications

Today, wireless power transfer (WPT) is used in many electronic devices such as laptops, smartwatches, mobile phones, and electric car charging. With there technological developments, remote wireless charging of devices will become more important soon. Considering the transmitter antenna design challenges for the WPT application, the main challenges are small dimensions to facilitate its placement in different platforms, steerable for receivers at different angles, high directivity (narrow beam), and high polarization efficiency. In this study, a circularly polarized WPT transmitter (antenna array) in the 5.8 GHz ISM frequency band is designed and optimized. An 8x8 phased array antenna is chosen to achieve high-power density and directivity. The antenna array dimensions are 19.2x19.2x0.2 cm with 64-unit cells. Parametric simulations are performed to achieve an axial ratio result below 0.58 dB and return loss (S11) of -18.70 dB. The antenna input impedance is 1.10 + 0.2233i on 5.8 GHz. By making an optimum unit cell, 8x8 Phased array is created, and the result of directivity at different angles is compared. The proposed phased array antenna achieved a 22.21 dB right-hand circular polarized directivity and 13.64-degree half-wave beamwidth. In the antenna beam steering step, the directivity result from 0 degrees to 45 degrees is compared. The individual return loss results and mutual coupling values between the unit cells' ports in the array antenna are examined. As a result of this study, the maximum power density result of the designed 8x8 phased array antenna has been analyzed. Power density has been calculated at the receiving points at a certain distance from the antenna. These distances are 1 meter, 3 meters, and 5 meters. The power density results of these distances at certain angles concerning the antenna are also studied. Results show that a relatively proper RF power density in receiver locations can be used for some application works.