Sharp detection, no noise: China tests breakthrough radar technology

During the tests, the silent Cessna, using the new radar tech, identified ground targets with over 20 decibels greater clarity than traditional techniques
New Delhi
In a breakthrough that could reshape the future of military operations, Chinese scientists have developed a radar system that can detect moving targets without making a sound — even in the noisiest environments.
The technology, developed by a team led by radar scientist Li Zhongyu, uses passive bistatic airborne radar and advanced signal processing to detect targets while remaining undetectable itself, reported South China Morning Post.
The test
Scientists in China tested a new type of radar technology using two small planes (Cessna-208 Caravans) flying in formation, separated by altitude. The one above sent out radar signals, and the other, flying silently below, gathered echoes without emitting any signals.
They aimed to detect three vehicles moving far ahead over uneven terrain covered with dense vegetation and structures. For traditional radar systems, detection in such conditions is difficult because radar signals bounce all over the place in these environments. This creates clutter on radar screens, making it difficult to distinguish actual targets.
Problems faced by traditional radar
When two radar units operate separately, the reflected signals from targets don't stay aligned—they get spread out over different distances, known as range migration. This scattering causes the target's signal to blur, making it harder to detect clearly.
Additionally, the Doppler effect, which helps identify moving objects, gets distorted as these frequency shifts spread over a wide range. This creates a lot of background noise that drowns out the actual signals from targets. Moreover, the unnecessary echoes change unpredictably depending on the distance, making it very difficult for conventional radar systems to filter them out effectively.
How the new radar solves them
The new approach uses three steps for clear detection:
Motion correction: The researchers used techniques called Keystone transform and high-order compensation to gather the dispersed target signals into precise range spots. This focused energy made the targets easier to identify, aided by a process known as motion correction.
Spectrum compression: This step refines blurred Doppler signals to sharpen the radar's ability to identify motion, improving target resolution.
Space-time decoupling: Their breakthrough technology, called the 'space-time decoupling two-channel clutter cancellation method,' uses a special matrix (a math formula) to separate the clutter's non-linear knots. By aligning spatial frequencies to zero while preserving relative speed profiles, it allows perfect cancellation of environmental clutter between dual-channel echoes.
During the tests, the silent Cessna identified ground targets with over 20 decibels greater clarity than traditional techniques, reported SCMP.
The first tests for this novel tech were conducted five years ago.
Military and strategic implications
If and when implemented, the new radar technology could help military planes spot targets — vehicles, ships, missiles — at long range without being detected, even through clouds or darkness.
Li's innovation also eliminates the exposure risks of low-probability-of-intercept (LPI) radars. LPI radars minimise the chance of being detected by operating at lower power levels or changing frequencies, but they still carry a risk of discovery.
'According to our knowledge, this is a world first,' Li claimed about the innovation.

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