A high-efficiency near-field focused transmitting antenna based on the equal power divisions

For microwave power transmission (MPT), the transmitting (Tx) array with a tapered amplitude distribution can achieve a maximum beam collection efficiency, but it needs a feeding network with an arbitrary power division ratio; thus, it is complicated and costly in practical applications. This work explores realizing high transmission efficiency by a Tx array with the equal-ratio steps amplitude distribution (ERSAD). By using the ERSAD, the amplitude value of the central units of the Tx array is uniform, and the amplitude feeding of the edge units only needs equal power divisions. Thus, the amplitude feeding is greatly simplified. Besides, a compensated phase distribution is used to focus the radiating beam on the receiving aperture. To validate the proposed design, a Tx antenna consisting of 8 × 8 units with a total aperture size of 1 × 1 m2 is designed. The operating frequency and the focused distance are 5.8 GHz and 10 m, respectively. A 64-way microwave power source is used to adjust the amplitude and the phase of the Tx array, and an MPT experiment is conducted. The measurement shows that, compared with the 10 dB Gaussian amplitude array, the proposed array nearly has the same transmission efficiency against different receiving apertures.