The Chinese claim that it can break the stealth technology that the F-35 Lightning II uses.

"Illustration of a Chinese device detecting U.S. stealth aircraft emissions (AI-generated, unrealistic). Credit: Ideogram." (Sustainability-Times/"China Can See the Invisible”: Beijing Unveils Handheld Tech That Locates U.S. Stealth Aircraft With Pinpoint Accuracy")

The fact is that there is a possibility of breaking the stealth technology that bases it on radio waves aimed in another direction. The traditional stealth base is that the radiation reflection is scattered. And radar gets minimum radiation reflection. This is the reason why the shape of the stealth aircraft is soft. 

If radar sends impulses straight from above, the stealth aircraft scatters that radiation around. This kind of effect is seen in the radar images that portray Venus's mountains. The white "shine" is the scattering radiation, that scatters from the mountains. Same way radar impulses scatter from the B-2 and B-21 bombers. If the radar is above the aircraft it sees that scattering the same way as radar sees scattering radiation from Venus's mountains. 

The scattering effect disturbs radar signals that reflect from the ground. The thing is that the same effect can be used to uncover stealth from all angles. But this requires a background reflector behind the target. 

The other version is that the system uses two aircraft. Those aircraft send radio signals to each other. And if the radiation scatters from somewhere. The system sees that scattering radiation. By sending impulses that reflect from that reflection. The radar reflection forms the radio halo around that object. 

Image: Wikipedia. 

Above radar image of Maxwell Montes, the highest mountain on Venus from the straight above. The white areas are formed by radar impulses scattering from the mountain and landscape. The white color is not snow. It's a reflection from the scattering radio waves. 

White color on canyons forms when a radar wave crosses them, and then the radar gets reflection from that radiation. So the white color forms when the radar impulses form the "dome" across the canyons. And then other impulses start to reflect for that radar dome. Same way stealth aircraft scatter radar signals. And that is the reason why there is a pyramid on the top of the modern stealth warships. The high-resolution radar can see that this reflection disturbs the reflection from around the warship. 

Things like sensor fusion, where AI connects sensors that use visible light, IR, laser scanners, lidars, and acoustic sensors together.  Those systems are the network of airborne, ground, and seaborne sensors that share their data with each other. The AI boosts the image recognition and the lidar and radars can see the jettison of the aircraft. 

The radar can observe things like carbon emissions from the engines, and it can use various systems to locate the stealth plane. The idea is that if the carbon dioxide or monoxide emission has a certain shape but not the source that the radars see can be a stealth fighter. Another way is to use things like nanoparticles that the radar sees. 

When a stealth fighter moves in the air, its pressure impulses and pressure waves push those particles. The system sees when stealth disturbs the particle cloud, even if it cannot see the stealth aircraft itself. Those nanoparticles can be the clouds that the system observes. 

However, the new types of stealth systems can base the idea that material absorbs all radiation that hits the target. The system can also conduct radiation into one point which can be the capacitor. There are materials. 

Which can absorb almost all energy that hits them. The problem with those materials is that they must put the energy into somewhere. Maybe the aircraft stores that energy into salt water and then pumps that water away. If those systems cannot pump their energy into somewhere that can cause damage to materials. 

High-power microwave transmitters can also protect targets against stealth technology. Those systems can be weapons that rotate 360 degrees. Microwave systems are developed to operate against drone swarms. They form a dome that the drone swarms cannot pass. But they can also operate against the aircraft. There is the possibility that the aircraft can protect itself using counter microwave radiation. 

Rotating microwave transmitters can also cause problems with stealth and other aircraft. When microwave transmitters send microwaves to the stealth fighter, that system warms those materials. And that can cause even destruction. Microwaves and laser systems can be the next-generation tools that can deny drone swarms and stealth aircraft operations. 

 https://www.sustainability-times.com/research/china-can-see-the-invisible-beijing-unveils-handheld-tech-that-locates-u-s-stealth-aircraft-with-pinpoint-accuracy/

https://commons.wikimedia.org/wiki/File:Maxwell_Montes_NW_part_crosseye-stereo.jpg