PLECS 3.7 Online Help

Discrete Fourier Transform

Purpose

Perform discrete Fourier transform on input signal

Library

Control / Discrete

Description

pict

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.

Parameters

Sample time
The time interval between samples. See also the Discrete-Periodic sample time type in section Sample Times.
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.

Probe Signals

Input
The input signal.
Magnitude
The first output signal, i.e. the computed magnitude.
Phase
The second output signal, i.e. the computed phase angle, in radians.