Antinull 2-D Waveguide Power Transfer Based on Standing Wave Diversity

We propose a phase-tunable and termination-switchable multiport feeding system for antinull 2-D waveguide power transfer (2DWPT). 2DWPT systems using an open- or short-ended waveguide sheet generate standing waves in the sheet. Because of the standing wave pattern, the efficiency of the power transmission to a receiver (RX) strongly depends on its position and it can drop to almost zero at some points, which are referred to as nulls. The proposed system is capable of changing the standing wave pattern. By selecting an appropriate standing wave pattern according to the RX position, null generation at the RX can be avoided. We refer to this concept as standing wave diversity. In the proposed multiport system, three diversity methods are implemented: port selection, termination selection, and constructive superposition diversity. The effectiveness of these methods is explained by simple theoretical analyses. Our experimental measurement results agree with the analysis results and demonstrate that the proposed system can eliminate nulls and improve the average efficiency of power transfer to arbitrary RX positions.