PLECS 2.1 Online Help

Discrete Fourier Transform

Purpose

Perform a discrete Fourier transform of the input signal.

Library

Extras/Discrete Analysis

Description

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This block calculates the discrete Fourier transform of a periodic input signal based on discrete samples. The sample time, the number of samples and the harmonic order(s) can be specified. The fundamental frequency f1   of the running window is

                  1
f1 = ----------------------------.
     sample time × number of samples

The outputs of the block are the magnitude and phase angle of the specified harmonics.

If you specify more than one harmonic, the outputs will be vectors with the corresponding width. Alternatively you can specify a single harmonic and feed a vector signal into the block.


Note  This block is only available for Matlab 7.0 or newer.

Parameters and Dialog Box

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Sample time
The time interval between samples.
Number of samples
The number of samples used to calculate the Fourier transform.
Harmonic orders n
A scalar or vector specifying the harmonic component(s) you are interested in. Enter 0    for the dc component, 1    for the fundamental component, etc. This parameter should be scalar if the input signal is a vector.