ABSTRACT
Some typical sources of electromagnetic emissions are transmitters, pulse generators, oscillators, digital logic circuits, switching power supplies and converters, relays, motors, and line drivers. The majority of unintentional emissions are composed of a great number of frequencies typically caused by switching and transient noise. Design engineers usually measure digital and impulsive signals in the time domain with an oscilloscope or a logic analyzer, whereas EMI specications and measurements are made in the frequency domain. Either Fourier analysis or Laplace transform may be used to compute the amplitude of the frequencies contained within the impulsive noise (the spectrum occupancy), or a spectrum analyzer or receiver may be used to measure the frequency components. Making a measurement is easier and more accurate, especially when the waveform is complex in shape.
