Antennas, often made of metal, are built to receive and transmit electromagnetic (EM) waves. As these oscillations wash through the metal cable, they shake up electrons within the antenna and produce an electric current.
Antennas 101
The current generates a voltage readout, which essentially “translates” EM information into an electrical language.
antennas only work if their length roughly matches up with the wavelength of the EM it picks up. In physics parlance, this is called “resonance.”
As a rule of thumb, a conventional antenna needs to be at least one-tenth the length of the EM wavelength that it’s picking up for a given frequency. The radio part of the spectrum encompasses relatively long wavelengths, anywhere from centimeters to meters. For the most commonly-used part of the radio-wave spectrum—say, cell phones—the antennas need to be at least a few centimeters long to reliably convey the message.
Antenna Theory
Understanding Electromagnetic Radiation
Acoustic antennas
Acoustic antennas turn EM waves into acoustic ones, which are then converted into voltages.
When matter jiggles, it produces these (sometimes inaudible) “sound waves.” Compared to their EM counterparts, acoustic waves are on a completely different spectrum—sound, not light. Because they travel much slower than light, their wavelengths can be orders of magnitude shorter for any given frequency (frequency = speed/wavelength). Acoustic resonance waves are roughly 10 thousand times—smaller than electromagnetic waves.
They work by using piezoelectric film.
Expect to see many new applications for this new technology in the next couple of years.