Getting a wireless signal through water has long been a headache. Engineers at the University of Florida say they have built a cheaper, lower-power way to do it, using a magnetoelectric antenna that can send and receive very low and low-frequency electromagnetic signals underwater.

The team published the work last month in the IEEE Journal of Oceanic Engineering. In tests, the system, called BlueME, communicated across 700 metres while operating at about 10 watts at maximum capacity.

“Our design benchmark was to keep power consumption very low, ideally lower than a standard stereo camera system, while maintaining robust communication performance,” UF computer scientist Md Jahidul Islam said in a university press statement.

“Our compact, energy-efficient BlueME system achieves that balance, operating around 10 watts of power at maximum capacity,” he said.

Islam and his colleagues, including University of Florida Department of Electrical and Computer Engineering assistant professor Adam Khalifa, tested the system with autonomous marine robots. The researchers said the work could help remote marine environmental monitoring, naval operations and offshore infrastructure inspections.

“Underwater multi-robot coordination remains extremely difficult because communication bandwidth and range are so limited,” Islam said.

“Today, many underwater robots can only exchange sparse status signals or rely on surfacing periodically to transmit mission data. That significantly limits real-time autonomy and coordination.”

Governments have used very low frequency systems to communicate with submarines from outside the water, but those systems have been large because the wavelengths can reach 100 kilometres. The University of Florida team said its smaller magnetoelectric antenna gets around that by using piezoelectric materials that resonate at specific very low frequencies regardless of antenna size.

The researchers tested BlueME in freshwater in Lake Wahlberg in Gainesville, Florida, and in saltwater in the open ocean.

“Ocean trials demonstrate that the system operates effectively under challenging conditions, such as turbidity, obstacles, and multipath interference, which are factors that typically degrade acoustic and optical methods,” the researchers wrote in the study.

Islam said compact underwater communication technology could change how autonomous marine systems work together.

“Advances in compact underwater communication could fundamentally change how autonomous marine systems collaborate and operate in complex ocean environments,” he said.

“We are talking about the very early days of a very powerful product.”

Khalifa said his medical device research helped shape the project. He had been working on small wireless medical devices designed to be injected instead of surgically implanted, and said those devices also face communication problems because the human body is mostly water.

“I’ve spent years designing miniature wireless implants and studying efficient power transfer in highly conductive environments,” Khalifa said in the university statement.

“At one point, it clicked that many of the same physical challenges inside the human body also exist underwater,” he said.

“Our body is effectively made of lightly salted water. That realization opened the door to thinking about ocean communication in a completely different way.”

The researchers have filed a provisional patent and said they want to refine the technology for use with more autonomous underwater vehicles.

“We demonstrated these results with very limited initial resources,” Khalifa said.

“With dedicated development and larger-scale deployment, the possibilities become much broader.”

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