In a revolutionary stride for modern naval warfare and communication, Chinese scientists have created a technology that could change the rules of submarine detection. The team, led by Li Daojing from the National Key Laboratory of Microwave Imaging, has developed a radar system capable of moving at near-light speed to detect submarines hidden deep beneath the ocean’s surface. Using high-energy microwave synthesis technology, they achieved the creation of a virtual, radio-emitting source in the sky—an innovation previously confined to science fiction. The scientists made this claim in a study published on November 25 in the Chinese academic journal Modern Radar.
This virtual source can emit electromagnetic waves while traveling at velocities close to the speed of light, unlocking new capabilities in underwater detection. The breakthrough leverages the Doppler effect, a well-known phenomenon where waves emitted by a moving object change frequency relative to the observer. As the source moves away from an observer on Earth, its electromagnetic waves stretch in wavelength, lowering their frequency and creating extremely low-frequency (ELF) waves.
According to the researchers, “Based on the Doppler effect of near-light-speed motion away from the observer, the signal frequency can, in principle, be significantly reduced, and the signal pulse width broadened.” This manipulation of wave properties allows ELF waves to penetrate seawater, making them uniquely suited to detecting submarines even hundreds of meters below the ocean’s surface.
The Role of ELF Waves in Advanced Detection
ELF electromagnetic waves, with their exceptionally low frequencies (as low as 100Hz) and long wavelengths (exceeding 100 meters), are central to this new detection method. These waves amplify the radar cross-section (RCS) of submerged nuclear submarines to up to 88 square meters, significantly enhancing their visibility to detection systems. According to the researchers, such targets can now be identified with “common magnetic detectors.”
To maximize efficiency, compact detectors can be mounted on drones, enabling “gradient detection of targets across the entire field,” the team wrote. This innovation presents an elegant solution for sweeping vast areas of the ocean and pinpointing hidden underwater threats.
Rethinking Antenna Design
Traditionally, ELF signal generation has required massive antenna arrays. For example, China’s mountainous ELF facilities use transmitting antennas exceeding 100 kilometers in length. Li’s team, however, has drastically reduced this requirement. By condensing the antenna length to just 100 meters, they have created a system that can be deployed easily aboard naval ships.
The system’s operation involves high-frequency, high-power electromagnetic waves emitted by these antennas, which converge in the atmosphere to form a virtual radio-emitting source. As one source moves away, another is generated, ensuring a seamless stream of ELF waves.
The SCMP wrote, “We employ an array structure to approximate high-speed motion Doppler signals in space through a stepwise manner, making equivalent near-light-speed motion possible.” This unique approach makes it possible to overcome the traditional limitations of ELF wave generation, opening up possibilities for more compact and efficient systems.
Applications Beyond Detection
While the primary application of this technology lies in detecting submarines, its potential extends far beyond. The system could revolutionize communication between surface ships and submarines. With an effective range of up to 6,000 kilometers, it offers an unparalleled method for transmitting signals over vast distances underwater.
Li’s team has already completed ground-based technical verification of the system and is now focused on further miniaturization. Their goal is to reduce the antenna length to approximately 30 meters, enabling even greater flexibility in deployment.
Collaborative Efforts and Future Prospects
The project is supported by major players in China such as China’s defence and research sectors, including the China Electronics Technology Group, a primary supplier of electronic warfare systems to the People’s Liberation Army, and Northwestern Polytechnical University, a prominent center for military technology development.
The implications of this research are immense. By combining theoretical physics with cutting-edge engineering, Li’s team has introduced a disruptive technology that could redefine underwater surveillance and military communication. Submarines—long considered the stealthiest component of naval operations—may no longer find refuge beneath the waves.
As the team continues to refine and enhance the system, it is clear that this innovation is poised to shape the future of naval warfare and communication. With each advance, the once-unreachable depths of the oceans come closer to being fully explored and monitored.