Results of a DC motor driving test with a power sent by a microwave and extracted with a rectenna array are reported. No significant difference has been observed in the output DC power from the rectenna array between a motor load and a resistive load. Mechanical output could be extracted from the received microwave power with an efficiency of 26%.

A rectenna element applicable to Stratosphere Radio Relay System was proposed and a fundamental microwave power transmission experiment was carried out at 2.45GHz using a rectenna array manufactured based on the proposal. The rectenna element consists of a circular microstrip patch and a rectifying circuit of novel balanced-type design. The circuit allows to mount a rectifier and circuit components just on one side of a substrate without through holes, and hence it must be easy to manufacture a rectenna even having a large aperture. It was verified by a preliminary experiment that the rectifying circuit can provide more than 1 W of DC output power using 8 Shottky diodes as a rectifier with microwave-DC conversion efficiency of 67%. Then, DC output power of 4W was obtained from the 4-element rectenna array in the microwave power transmission experiment carried out in a radio anechoic chamber. The data showed a feasibility of practical application of the microwave power transmission technique.