Mechanical radio transmitter technology could be game changer for low-frequency communication

Assistant Professor Gaurav Bahl will lead a team of engineers that aims to develop mechanically enabled ultra-low frequency (ULF) transmitters for digital communications in the 100 Hz to 1 kHz frequency range.

Bahl, MechSE Assistant Professor Sam Tawfick, and ECE Professor Jennifer Bernhard’s $1.5M proposal, “Magnetic Communicator via Resonant Oscillating Bar-magnets with Energy Recovery,” is in response to a new program from DARPA (Defense Advanced Research Projects Agency), called A Mechanically Based Antenna (AMEBA), that aims to explore new ways of developing radio transmitters.

The fundamental challenge with using traditional antenna technology for generating ULF signals is the direct relationship between the electromagnetic wavelength and the antenna size. At such low frequencies, the wavelengths are hundreds or thousands of kilometers, which simply forbids the construction of low-power portable antennas.

The researchers said they believe the answer lies in revisiting the fundamental question of how electromagnetic waves are produced. An electronic antenna is simply a resonator that accelerates electronic charges along a determined path. This can also be achieved mechanically—that is, by simply accelerating a charged object or a permanent magnet. These mechanical antennas could be thousands to millions of times more efficient than their electronic counterparts at ULF frequencies. As a result, their AMEBA funding will help them develop such ultra-efficient mechanical transmitter systems and establish their feasibility.

Access to radio frequencies at the very low end of the electromagnetic spectrum could open previously impossible communication channels for use in both civilian and defense operations. ULF signals are able to penetrate water, metal, soil, rock, and building materials, so they are potentially very useful for situations where conventional radio communication is impossible.

“If we are successful, scuba divers would be able to use a ULF channel for low bit-rate communications, like text messages, to communicate with each other or with nearby submarines, ships, relay buoys, UAVs, and ground-based assets. Through-ground communication with people in deep bunkers, mines, or caves could also become possible,” said Troy Olsson, AMEBA program manager at DARPA.

Bahl, the PI, will lead the team’s dynamics and microfabrication work, co-PI Tawfick is the precision manufacturing lead, and co-PI Bernhard will lead the electromagnetics and modulation effort.