Chinese scientists have achieved a breakthrough in submarine detection by creating a radio emission source in the sky using high-energy microwave synthesis technology.

This virtual signal source, which can be called ghost radar, can continuously emit electromagnetic waves while traveling at close to the speed of light.

This is what scientists claim in a study published on November 25 in the Chinese academic journal Modern Radar.

ELF waves can detect submarines at depth

Extremely low frequency (ELF) electromagnetic waves, capable of penetrating seawater, enable the detection of submarines hidden hundreds of meters below the surface.

According to the research team led by Li Daojing from the National Key Laboratory of Microwave Imaging of the Chinese Academy of Sciences, this breakthrough is a “disruptive technology.” the South China Morning Post writing.

Scientists explained that when exposed to signals with frequencies as low as 100 Hz, the radar cross section (RCS) of a nuclear submarine in seawater can reach up to 88 square meters (947 square feet). This makes it possible to detect underwater targets using “common magnetic detectors,” as Li and colleagues noted in their study. By installing these compact detectors on drones, they suggest it is possible to “achieve gradual detection of targets across the entire field”.

ELF signals, with wavelengths longer than 100 meters (328 feet), typically require large distances between antennas. Traditionally, generating low-frequency signals required massive antennas, such as the ELF facility in central China, which has antennas more than 100 km (62 miles) long.

In contrast, Li’s team reduced the length of the transmitter array to about 100 meters (328 feet), making it easy to install these antennas on Chinese navy ships. The high-frequency, high-power electromagnetic waves emitted by these antennas converge in the sky to create a virtual source of radio transmission. When one source dissipates, another is instantly generated, ensuring a continuous flow of low frequency signals.

Simulating near-light speed motion using spatial Doppler signals

The team explained that it uses a network structure to approximate Doppler signals of high-speed motion in space step by step, making motion close to the speed of light possible. Subsequently, the signal frequency can be significantly reduced and the signal pulse width can be widened.

The Doppler effect occurs when the frequency of a wave received by an observer differs from the source frequency due to relative motion. As the source and observer get closer, the observed frequency increases, and as they move further away, the observed frequency decreases.

This technology also has potential applications for communication between surface ships and submarines, with a range up to 3,700 miles (6,000 km), according to scientists’ calculations.

The technical ground verification has already been completed and Li mentioned that the next step would be to further shorten the length of the transmitter array to around 30 meters for more flexible applications.