By making use of the overlapping symmetries between the modal inlet fields and the engine face, it is found that the radar modulation due to a set of rotating blades can be computed using only one solution for any blade position. Frequency domain solutions for the stationary engine face can immediately produce modulation data with a simple postprocessing step. The validity of the modulation scheme is demonstrated with the aid of a simplified engine model possessing a semianalytical mode-matching solution. ¿ American Geophysical Union 1996