How is a plane wave seen by an observer in circular motion at constant angular velocity?

The response of a detector carried by an observer in a circular motion at a constant angular velocity to an incident plane wave is considered here. It is shown that, despite a formal analogy with Unruh effect, a power spectrum is obtained, which is very different from the thermal one. We find a discrete spectrum depending on the frequency of the original plane wave and on the frequency of the rotating motion of the observer. We propose a possible experiment to verify the predicted effect using Josephson junctions.