2-D Van Atta Array of Wideband, Wideangle Slots for Radiative Wireless Power Transfer Systems

We present a 2-D Van Atta array for far-field wireless power transfer systems. The antenna array is made up of wideband, wideangle long slots. The monostatic radar cross section (RCS) of the finite array is derived by windowing the aperture field distribution of the corresponding infinite case. It is shown that for oversampled apertures, the array behaves as an ideal Van Atta reflector. Therefore, the proposed solution can collect and reradiate the total power impinging on it from a remote source over a large field of view and bandwidth. The array design is presented and validated through measurements over a relative bandwidth of 24% centered at a frequency of 5.8 GHz. The array consists of four slots, each fed by eight coaxial ports. Coaxial cables are used to connect pairs of feeds in a Van Atta configuration. A bidirectional amplifier is also introduced into the Van Atta scheme to amplify the collected energy before retransmission to a possible moving user for wireless power transfer. Off-the-shelf components are used to implement the bidirection amplifier. The amplifier is matched across the bandwidth of the array and provides 5 dB gain. Monostatic RCS measurements show that the array exhibits -10 dB beamwidths of about 118° and 80° in the E- and H-planes, over the entire bandwidth. In addition, it is shown that when the array ports are terminated with matched loads, the antenna RCS is reduced by approximately -15 dB with respect to the Van Atta case. This experimentally confirms that the array collects the total energy impinging from a remote source.