TABLE OF CONTENTS The Fourier transform technique was developed by J.B.J. Fourier (1768 1830) to assist in solving problems in heat conduction [4], but is so powerful that it has become very widely used by physicists and engineers and can be applied to a whole range of problems. In the present sphere of interest it is the means by which one can transpose data between the frequency and time domains. This will allow EMC designers and test engineers to view information contained in a signal from the point of view of both domains and thus achieve maximum understanding of it. The examination of prominent amplitude peaks in a spectrum and their comparison with dominant waveform features can lead to an insight into the type of circuits which arc generating the interference signal. This is particularly useful when carrying out design or diagnostic EMC testing.
Fourier series, Fourier transforms, Laplace transforms and convolution theory are all linked mathematical ideas which shed light on the relationship between the frequency and time domains. The subject is wide and detailed, with whole texts such as that by Bracewell [3] devoted to its explanation. Clearly, in this chapter there is no space to do other than give some of the concepts involved and to state the formulas which apply. Understanding Fourier transforms is so important to being able to understand both frequency and time-domain data that the reader is urged to undertake additional study by recourse to the References.
The central...
