Chinese naval scientists say they can use other countries’ military radar to locate, track ships in new research

Researchers say new technology can use signals from radars, warships or even early warning planes of other countries to track cargo ships
Set-up uses simple gear such as a laptop and an antenna to disentangle the radar signals of foreign militaries, team says in recent paper

Science

Stephen Chenin Beijing

Published: 4:09pm, 7 Jan 2024

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Borrowing a blade to slay, an old Chinese proverb, speaks of using another’s weapon against them. Now, scientists from China’s navy say they have applied this ancient wisdom to today’s technology-driven wars.

The team, from China’s eastern Shandong province, says it has developed a technology that could use the signals emitted by the radars, warships or even early warning planes of other countries, to track cargo ships on the high seas. And it only requires simple gear such as a laptop and small antenna.

“The images were clear as day,” wrote Song Jie, a scientist at the PLA Naval Aviation University, in a peer-reviewed paper with his colleagues from Yantai University, both based in the coastal city of Yantai. Their findings were published in the Chinese-language journal Radio Science and Technology on December 20.

This feat was once considered impossible. Since the invention of radar in 1935, only the sender or their allies could use its signals. Using electromagnetic waves to locate targets requires knowledge of detailed physical parameters that are known only to the transmitter – and these are constantly changing.

The team says their simple detection set-up “works well for slow-moving targets at sea”. Photo: PLA Naval Aviation University

To outsiders, these signals appear as a tangled mess, and extracting valuable information from them would be like finding a needle in a haystack.

But Song’s team managed to use potentially non-friendly radar signals to detect ships going into and out of ports, an unprecedented feat.

“Our system works well for slow-moving targets at sea,” the team said. “It can track ships with ease.”

For countries like China, with vast radar networks, this might not be a game-changer. But for smaller nations or forces whose radars are destroyed or not affordable at all, this could be a lifesaver. By hijacking enemy signals, they could gain a crucial advantage with little effort.

Imagine the Houthis in Yemen, attacking cargo ships with drones or missiles. The United States blames Iran for passing intelligence about these ships, but what if the Houthis used American radar signals instead? Song’s team has proved this is technically possible.

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In Yantai, the scientists chose a residential building as the base for their experiment. By the window, a receiving antenna – not much larger than a clothes-drying rack – stood ready. Connected to this antenna was an electromagnetic wave analyser, about the size of a microwave oven, which processed the signals received. These signals were then fed into an ordinary laptop for further analysis.

The set-up was simple: all the equipment could be sourced easily and transported in the boot of a car.

Detecting targets at sea using radar is notoriously challenging due to the constant flux of electromagnetic waves reflecting off the waves, which often drown out crucial information amid the noise. But Song’s team was still able to locate and track all commercial ships sailing within 20km of the shore – a distance comparable to that between the Red Sea shipping lane and Yemen’s coast.

Moreover, they gathered vital intelligence on the direction and speed of the ships, invaluable for potential drone or missile attacks.

Although the signal source in the experiment came from a Chinese military radar, Song’s team did not use any technical parameters related to the radar.

This meant that, in real-world scenarios, their system could harness signals from any country’s military platforms.

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In their paper, Song and his colleagues shared their powerful algorithm, explaining how they used it to reverse-derive the operating parameters of a military radar from the received spectrum.

But practical applications presented their own set of hurdles. For instance, the direct signal from the radar to the receiving antenna was significantly stronger than that reflected off a ship’s hull, often masking the latter’s distinct characteristics. Both signals are crucial for accurate positioning. Also, disentangling them required a unique processing approach not typically found in standard radar stations.

Song’s team meticulously detailed these processes and precautions in the paper, along with insights on data compression and accumulation techniques that enhanced the speed and accuracy of the computer analysis.

The researchers believe their work could also assist the Chinese military in electronic warfare, with potential applications in electronic reconnaissance, anti-radiation weaponry, ultra-low altitude penetration missions and stealth technology.