Available Technologies

Background

In recent years, more and more IoT devices such as sensors and cameras have been installed in a factory and a facility, and retrodirective microwave power transmission has been attracting attention as a means for supplying power to these devices. In this method, the power supply device estimates the direction of the receiving device based on the signal emitted from the receiving device (pilot signal) and transmits power by emitting a microwave beam (power transmission signal) in that direction. However, this method has several drawbacks. First, the receiving device requires the system to transmit the pilot signals in addition to the power receiving system. Next, the power of the receiving device is required to transmit the pilot signal beforehand. Lastly, the interference between the pilot signal and the power transmission signal makes it difficult to accurately identify the direction of the receiving device.

Description and Advantages

Researchers at Kyoto University solved the abovementioned drawbacks by adopting the second harmonic re-radiated by the receiving device (Rectenna: rectifying antenna) in response to the power transmission signal for the pilot signal. This invention is a good fit for applications that require minimizing the weight of the receiving device and ones that transfer power to the fast-moving receiving devices.

• Generating a pilot signal without using power from the receiving device

Generating the pilot signal does not consume power from the receiving device. Therefore, power can be transferred to the receiving device even when the receiving device runs out of battery power.

• No interference between the pilot signal and the power transmission signal

Because the pilot signal and the power transmission signal have different frequencies, they do not interfere with each other and the direction of the power receiving device can be accurately determined.

• Compact and lightweight power transmission device

The pilot signal receiving antenna and power transmission antenna can be integrated into a single unit, and the conjugate circuit is a simple analog circuit, making the power transmission device compact, lightweight, and low-cost.

• Capable of transmitting power to multiple power receiving devices or to the power receiving devices moving at high speed

Since the directional identification of power receiving devices is performed by a simple analog circuit, it is possible to transmit power to multiple power receiving devices or to a power receiving device moving at high speed.