where 𝑃𝑟Pr is the received power, 𝑃𝑡Pt is the transmitted power, 𝐺𝑡Gt and 𝐺𝑟Gr are the gains of the transmitting and receiving antennas, respectively, 𝜆λ is the wavelength of the signal, and d is the distance between the charging station and receiver. The server ...