Simplified Prediction of Conducted and Radiated Interference Levels for Pulses and Step Functions

A series of laboratory measurements were made by the Bell Aerosystems Company to measure the levels of interference conducted by and radiated from shielded and unshielded signal wires which carry pulses or step functions. These test data have been plotted into graphs which show the interference level in dB/1¿ V/Mc/s vs. frequency for many common rise/fall times, amplitudes, pulse widths, and wire lengths. These graphs provide a rapid method for comparing the interference spectrum of a pulse or step function with the limits specified by MIL-1-6181D and MIL-1-11748B. The necessary amount of wire or case shielding can then be easily determined by observation of the applicable graph.