Chinese researchers have developed a new substance that could be used to coat airplanes and make them essentially undetectable by radar by detecting and adapting to different frequencies, according to research published last week in the Journal of Applied Physics.
The material is known as an “active frequency selecting surface” or AFSS, and as Ars Technica reported, it involves a substance currently used in printed circuit boards that can be tweaked to absorb microwaves at a range of different frequencies. If used on a stealth aircraft, it could make it more difficult for currently available radar technology to detect the plane.
Currently, most stealth aircraft hide from radars by either using unusual body geometry to reflect radio waves, or by using materials that convert waves to heat and then absorbing them, according to Popular Science. The technique described by the Chinese scientists is different in that it uses a material that tunes itself in order to protect against even ultra-high-frequency (UHF) radar.
Researchers reported that the AFSS makes it possible to absorb radio frequencies ranging from 0.7 to 1.9 gigahertz (GHz), reducing reflectivity by anywhere from 10 to 40dB, according to Ars Technica.
So how does it work?
The material has been “loaded with lumped elements” that allow it to tune the frequency range, the researchers explained. Reports indicate that it uses varactor diodes, which are semiconductor capacitors often used in electronic tuners, and PIN diodes, which are semiconductors capable of acting as resistors to electromagnetic radiation at radio and microwave frequencies.
Building upon previous research in the field, the authors of the new paper developed an ultra-thin material measuring less than eight millimeters in thickness—including an 0.8 millimeter layer of a circuit board material known as FR4, a 0.04 millimeter layer of copper-and-semiconductor AFSS underneath that, along with a 7.0 millimeter honeycomb material for support.
By publishing their findings, the authors remove “a major obstacle for other countries that may want to build their own stealth fighters,” while also making it “easier for anyone trying to break stealth protection like this, as they have the technique available publicly… to find flaws” in the system.
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Feature Image: Wikimedia Commons
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