Tiny Membrane-Based Antennas

Illustration: Northeastern University/Nature Communications
Illustration: Northeastern University/Nature Communications

New membrane-based antennas could be nearly 100 times smaller than the most compact current antennas, a new study finds.

These antennas could find use in portable wireless communications systems, including wearable electronics, smartphones, bio-implantable antennas, bio-injectable antennas, bio-ingestible antennas, and the Internet of Things, researchers say.

State-of-the-art compact antennas are designed to resonate at specific wavelengths. But their miniaturization is limited to roughly one-tenth of their resonant wavelengths.

The new antennas developed by researchers at Northeastern University and their collaborators can now be shrunk to sizes as small as one-thousandth of the wavelength they aim to receive and transmit—without any degradation in performance. The researchers detailed their findings online today in the journal Nature Communications.

These new antennas consist of thin membranes made up of two different kinds of films. Its piezomagnetic iron-gallium-boron layers convert mechanical oscillations to magnetic signals and vice versa. They are paired with piezoelectric aluminum nitride films, which convert mechanical oscillations to electrical signals and vice versa.

When these membranes receive electromagnetic signals, their magnetic layers sense the magnetic fields of these electromagnetic waves. This causes the membranes to vibrate, which piezoelectrically generates a voltage.

Conversely, in order for the antennas to transmit, they vibrate. This causes the magnetic layers of the membranes to generate a magnetic current that radiates electromagnetic waves.

The sizes of these “magnetoelectric” antennas depend on the wavelengths of the acoustic vibrations they operate with instead of the electromagnetic signals they receive and transmit. Because these acoustic wavelengths are about 100,000 times shorter than their corresponding electromagnetic wavelengths, these new antennas can be much smaller than conventional antennas.

“This acoustic antenna concept changes the fundamental principle on which antennas have been designed for over a century, and can lead to dramatically compact antennas with improved performance,” says study senior author Nian-Xiang Sun, an electrical engineer and materials scientist at Northeastern.

In experiments, these nanoelectromechanical system (NEMS) antennas could receive and transmit at VHF and UHF radio frequencies. In addition, they are completely passive, requiring simple electronics and no battery.

Future research will attempt to improve antenna performance through new materials, new designs and better fabrication processes, Sun says. “These are the first magnetoelectric antennas that have been demonstrated, which are not perfect,” he says. “We see a lot of room of improvement.”


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