Open-ended voltage multipliers for wireless transmission of electric power

This paper presents a class of open-ended voltage multipliers, of which the input is a displacement current from a Goubau line and the output is a multiplied DC voltage. When terminated with a 500 ohm load, the proposed voltage multipliers have rectified a microwave power at 20 dBm into a DC voltage 5–6 V, corresponding to a conversion efficiency of approximately 50%. The maximum voltage reaches 20 V if the circuit is unloaded. Due to its characteristic impedance being comparable to that of the free space, the Goubau line feeding the proposed voltage multipliers has been successfully used as a monopole antenna for capturing ground waves in an experimental system for wireless power transfer. Over a short range, with r ≪ 1.05 m, the open-ended voltage multipliers vertically mounted on the surface of a lossy dielectric material were at best able to generate a power proportional to 1/r^0.4, where r is the distance between the receiver and the transmitter, suggesting that the received power is not a pure space wave.