Study on Power Conversion Efficiency of Rectenna Array with Deformed Flat-Top Beam for Microwave Power Transmission
Flat-top beam is a type of power beaming for microwave power transmission. This beam is beneficial to extract the maximum output power and power conversion efficiency (PCE) from rectifying antennas (rectennas) and suitable for drone applications because it requires substantial amount of dc power. In this paper, it is investigated in simulations and measurements how much influence a deformed flat-top beam has on the PCE performance of four-element and 16-element rectenna arrays. The flat-top beam was radiated from a 196-element transmitting antenna array and received by a 16-element receiving antenna array. Received power measured on the antenna ports was deformed from an analytically designed flat-top beam due to change in the transmission distance and polarization mismatch. The simulated combination loss of the rectifier array was kept less than 0.1 dB when CV was less than 0.2. Actual power loss after arraying became larger when the rectifier array was attached to the antennas. Since the developed rectifier element was efficient in the range of input power from 1.5 W to 3.3 W, it is necessary to illuminate the whole plane of the rectenna array with that power range while keeping CV of received power less than 0.2 at least.