How can that be passive? That statement doesn’t sound right to me.Would passive signal relay points be of any use, kinda like extenders that send back information ?
If it is relaying signal, then it is active.
Radar is a device that operates in electromagnetic domain. If you are sending signals then you are active.
Aesa radars do that cleverly by sending signals in rotating frequency pulses.by spreading signals across a wide frequency range and by rapid frequency shifting, and by using low probability intercept modes by emitting signals that are very weak and difficult to detect, minimising the chance of being intercepted by enemy sensors, they can be stealthy.
So if we go by the example given in that post; tower A and tower B sending and receiving signals with their Aesa radars, their detection would be difficult and they may be able to detect a stealthy plane that passes through their signal.