I wish I could remember more specific details and terminology, but 10-15 years ago a friend working at an economic development agency asked me to look over a patent invention submitted by some Los Alamos researchers. I was in no way properly qualified to understand the physics, but it nominally involved a faster than light component, and he thought he'd run it past me to reduce the chance he looked foolish when putting it to more qualified people.

The patent was based on research analyzing the propagation of wavefronts on neutron stars[1]. I forget the term(s), but the critical aspect related to features which travel along the wavefront faster than light. This feature couldn't actually be used to communicate faster than light, obviously, however the patent claimed to be able to use it to defeat active radar jamming--more specifically, radar deception. Because this controllable wavefront feature (modulation? polarization?) could be FTL, and the waves themselves light-speed, it was thus intrinsically impossible to fake a correct return signature.

From a lay geek's perspective, I told my friend that AFAICT this aspect of the invention seemed not obviously flawed: it was FTL only in the sense that you could swing a flashlight across the moon and the apparent motion of the reflected beam could be faster than light. Normally such a phenomenon is merely a curiosity, but apparently the inventors had put it to some practical use, at least in theory.

[1] IIRC, either physical or magnetic waves generated by starquakes.

I'm guessing they were referring to phase velocity:

https://en.wikipedia.org/wiki/Phase_velocity

You can see the effect shown in the first animation of this article if you keep track of the wave peaks in the wake of a boat. They start at the back of the group of waves, move through it, and fade away as they reach the front.

https://www.youtube.com/watch?v=lWi_KpBy8kU