US researchers harvest microwaves with a meta-material

Engineers at Duke University North Carolina have designed a meta-material that harvests microwave power.

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“Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting,” said Professor Steven Cummer. “The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power.”

The design, see photo, operates at 900MHz. Maximum harvested power occurs for a resistive load close to 70Ω in both simulation and experiment on the five cell copper-and-fibreglass array, which can convert at 36.8% efficiency, said the university. A separate PCB changes the received microwave signal into dc – at around 7.3V in the photographed set-up.

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Engineering students Alexander Katko (left) and Allen Hawkes show a their harvester powering a green LED. It is within a waveguide, driven through the coax on the left.

“We were aiming for the highest energy efficiency we could achieve,” said student Allen Hawkes (right in photo). “We had been getting energy efficiency around 6 to 10%, but with this design we were able to dramatically improve conversion.”

“The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas,” added Alexander Katko (left in photo). “When traditional antennas are close to each other in space they talk to each other and interfere with each other’s operation. The design process used to create our metamaterial array takes these effects into account, allowing the cells to work together.”

There is a paper in the microwave harvester in Applied Physics Letters.

The research was supported by the US Army.


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