Coherence Functions Used to Define Sources of Airborne Antenna Vibration.

Conditional coherence functions are used in a practical mechanical vibration problem to determine which of several possible inputs are the major causes of vibration of an airborne antenna. Pairwise, multiple, and multiple conditional coherence spectra are derived from flight vibration data. The vibratory inputs causing several important antenna responses are identified despite correlations between inputs. These inputs offer the highest potential for reducing the antenna vibration by isolation or decoupling. The results also provide a measure of the vibration reduction which can be achieved by eliminating these inputs.