Microwave power transfer provides power wirelessly by converting electromagnetic waves emitted by an antenna to DC power using a rectifying antenna (rectenna). We are developing a distributed cooperative power transfer system that intentionally generates constructive interference on a device by applying appropriate phase control to microwaves emitted from each antenna to improve the efficiency of the power supply. This paper proposes a novel phase optimization method to find the optimal phase that maximizes the received power of the device. The proposed method obtains the optimal phase by performing nonlinear curve regression based on the received signal strength indication (RSSI) feedback of the device. Experimental evaluations showed that the proposed method improved the stability of the supplied power and reduced the time of phase optimization in both feedback models.
An in-phase/anti-phase triple-feed array antenna employing two types of magic-Ts is proposed. The proposed array antenna effectively provides three radiation patterns in both E-and H-planes with a simple structure. In this paper, design and operating principles of the proposed array antenna is presented with simulation results to highlight its features. The proposed array antenna can be used for many kinds of advanced antennas such as direction-of-arrival estimation antennas, beam steering antennas and wide-angle rectennas.
A stochastic model of arm swing is proposed for standard test of rotational energy harvester (EH). Based on the mean values and standard deviation of the frequency and amplitude of arm swing from walking experiment, the output power of rotational electret EH for 95 % coverage is estimated for different parameters of the frequency and amplitude. A multi-link robot is also introduced to mimic the arm swing motion precisely under various conditions. It is found that the output power for the maximum frequency and amplitude is 2.5 times higher than that for the mean values, and the present stochastic model gives 22% higher output power than that with mean values.
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