Others have already commented, but normal surveillance radar is like a spotlight from the tower. It goes around and scans the area. If they determine that you are important, the radar can "lock on" to you which means that it will no longer scan around but would shine the light on you constantly.

If they want to shoot at you, they turn on another even stronger more focused light to improve accuracy.

Military today have ability to detect enemy targetting radars and when they lock on so having such a thing in SciFi does not seem strange to me.