New antenna design promises tinier wireless devices

Technology News | September 21, 2017

By Rich Pell

Sensing / Conditioning Wearables Materials & processes Wireless Communications Analog Medical Electronics RF transmission

Antennas – a critical component in wireless devices – have not kept pace with the ever shrinking size of other electronic components – a result of their needing to be physically comparable in size to the electromagnetic (EM) wavelengths with which they resonate. Smaller antennas, say the researchers, would have big implications for Internet of Things (IoT) devices, cellphones, and satellites, and in the biomedical field could lead to better bioinjectible, bioimplantable, or bioinjestible devices.

“A lot of people have tried hard to reduce the size of antennas. This has been an open challenge for the whole society,” says Nian Sun (pictured), professor of electrical and computer engineering at Northeastern. “We looked into this problem and thought, ‘why don’t we use a new mechanism?'”

Addressing this miniaturization challenge, the researchers found a way to design antennas using an antenna’s acoustic – rather than electromagnetic – resonance. By tailoring the antennas to the desired acoustic resonance waves – which are roughly 10 thousand times smaller than electromagnetic waves – the antennas can be made one or two orders of magnitude smaller than the most compact antennas available today.

The key to the design is converting incoming EM waves into their acoustic equivalent. To do this, the researchers used a piezomagnetic material – which expands and contracts when exposed to a magnetic field – to efficiently convert EM waves to acoustic vibrations.

The piezomagnetic material itself is attached to a piezoelectric material, which converts the acoustic vibrations to an electrical signal. The process works in reverse when the antenna is sending out a signal.

According to the researchers, the new antennas would not only still work for cell phones and other wireless communication devices, but in experiments they found that their antennas performed better than traditional kinds. When they tested one of their antennas in a specially insulated room, they found that it sent and received 2.5-GHz signals about 100,000 times more efficiently than a conventional antenna of the same size.

Looking ahead, one application the researchers say neurosurgeons are interested in exploring is a device that could sense neuron behavior deep inside the brain. “Something that’s millimeters or even micrometers in size would make biomedical implantation much easier to achieve, and the tissue damage would be much less,” says Sun.

For more, see “Acoustically actuated ultra-compact NEMS magnetoelectric antennas.”