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Dran-View 6 User Guide

Chapter 19. Notes and Appendices

19.1. Notes on Harmonics

How does Dran-View do harmonic analysis?

19.1.1. Harmonic Analysis -A Brief Overview

The essential concept of harmonic analysis is that a band limited, periodic, time

domain signal may be equally expressed as a summation of harmonically related

sine and cosine functions. To do this, the harmonic amplitudes and phase angle

offsets of the sine/cosine functions must be chosen properly. We refer to the

process of decomposing the time domain signal (the waveform) into amplitude and

phase components as harmonic analysis. Dran-View transforms the selected (see

Area Marker tool), or if no time range has been selected, the visible part of a

displayed time domain (Waveform) signal into its equivalent amplitude and phase

components by doing a Fourier Transform. This function is invoked by insertion of

a DFT Chart, a Text Label containing either the $DFTDETAILSFULL or

$DFTDETAILSBASIC control codes, or a Phasor. Multiple cycles of the

fundamental may be analyzed to achieve better averaging or interharmonics.

Using an appropriate sine/cosine series summation, the original time domain signal

(the waveform) may be approximately reconstructed from the provided phase and

amplitude information. The full set of required harmonics coupled with infinite

arithmetic accuracy would make it theoretically possible to regenerate the signal

exactly. The number of harmonics required to do an “ideal” reconstruction would

be N divided by two, where N is the number of samples in the highlighted sample

window.

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Dranetz Guide Guia do Utilizador Página 208