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Ground demonstration testing of microwave wireless power transmission

JAXA conducted a R&D program toward the development of a wireless power transmission technology for SSPS (with a focus on high-accuracy microwave beam-pointing-control technology) in cooperation with Japan Space Systems (J-spacesystems), an incorporated foundation consigned by the Japanese Ministry of Economy, Trade and Industry to carry out the Solar Power Wireless Transmission Technology Development Project.

This R&D program aims to develop a microwave wireless power transmission technology critical to the success of the SSPS program. Without the development of a technology to efficiently transmit high-power microwave beams toward the terrestrial power receiving system spot on, we will never be able to achieve our goal of realizing SSPS and using it to diversify the energy sources available to our planet. At present we have been conducting ground tests of microwave wireless power transmission employing a retrodirective system. A pilot signal is sent from a pilot-signal-transmitting antenna mounted on the terrestrial-power-receiving antenna panel to pilot-signal-receiving antennas mounted on the orbital-power-transmitting antenna panels. Each phased array antenna panel receives the signal, calculates the necessary phases for its microwaves, and adjusts the phases accordingly.

We conducted the ground demonstration tests sketched out below for the development of a high-accuracy microwave beam-pointing-control technology. We were able to transmit “wireless” electric power enough to make domestic contacts by amateur radio station via JA3YBB.

 
 
Power receiving antenna In the operational SSPS scenario, it will serve as a ground-based antenna to receive microwaves transmitted from the SSPS and convert them to electricity.
Power transmitting antenna In the operational SSPS scenario, it will serve as an antenna mounted on an SSPS satellite to transmit microwaves to the ground.
Pilot signal A signal sent from a pilot-signal-transmitting antenna mounted on the terrestrial-power-receiving antenna panel to pilot-signal-receiving antennas mounted on the orbital-power-transmitting antenna panels so as to control microwave beam for power transmission into its arrival direction.
Phased array antenna An antenna array in which a desired beam shape and beam pointing can be produced by controlling and synchronizing the phases and amplitudes of microwaves sent from each antenna element of the array.
Retrodirective technology A technology capable of detecting the direction of a pilot signal and controlling microwave beams for power transmission toward it.
 

Results

In cooperation with the J-spacesystems, we succeeded in the wireless transmission of power strong enough to communicate by amateur radio between Ako and other locations.

We appreciate the cooperation extended by Ako Amateur Radio Club and other participating operators.

 
Test date and test site
  • Date: 10:15 to 16:45, March 8, 2015
    *The ground demonstration test was initially scheduled for March 1, 2015 but was postponed because of rain (the test apparatus is not waterproofed).
  • Site: Mitsubishi Electric facility in Hyogo Prefecture
 
Research on Microwave Wireless Power Transmission Technology
Outline of ground demonstrations of microwave wireless transmission test
 
Photos of the ground demonstration of microwave wireless transmission

JAXA Digital Archives/ Photo Archives

 
Test configurations
Transmit frequency 5.8 GHz
Transmit power Approx. 1.8 kW
Receiving power Approx. 320 - 340 W
*1: The power is equivalent to the power transmitted with no positional displacement between antenna panels.
*2: Approx. 85-95 W when the transmission phase is not electronically altered to offset the displacement
Transmission distance Approx. 55 m
Number of amateur radio contact
(40 m Band)
283 contacts by Ako Amateur Radio Club JA3YBB (including the stations at the rehearsal)
 
 
All participants (We appreciate the cooperation)