# FFT Analyzer

Perform Fourier analysis of simulation data signals

## Description

The **FFT Analyzer** app allows you to perform Fourier analysis of
simulation data and provides access to all the simulation data that are defined as
structure-with-time variables in your workspace. The app displays the spectrum as a bar graph
or as a list in percentages relative to a base value or to the DC component of the
signal.

## Open the FFT Analyzer App

powergui Block Parameters dialog box: On the

**Tools**tab, click**FFT Analysis**.MATLAB

^{®}command prompt: Enter`powerFFT`

## Parameters

`Structure with time (click to update)`

— Refresh simulation data variables

button

Refreshes the list of simulation data variables in the **Structure with
time** drop-down menu. Refreshing allows you to import additional simulation
signals from the workspace without the need to close and reopen the tool. If the
workspace contains no structure-with-time variables, the drop-down menu shows Empty
list.

`Structure with time`

— List of simulation data variables

Empty list (default)

Lists all the simulation data variables that are present in your workspace. Use the drop-down list to select the structure-with-time variable that you want to analyze. If the workspace contains no structure-with-time variables, the list shows Empty list. Structure-with-time variables are generated by the Scope and To Workspace blocks in your model.

`Signal`

— Selected signal

no default

Lists the signal of the structure-with-time variable specified in the
**Structure with time** drop-down menu. Structure-with-time variables
that have multiple signals can be generated by a Scope block that has
multiple input ports. The list shows the name of the signals as they are labeled in your
models. If a signal is not labeled, such as the third signal of Scope2 in this figure,
the list shows unnamed (input 3).

`Dimension`

— Index of selected signal

no default

Indicates the index of the signal specified by the **Signal**
parameter. For example, the **Dimension** parameter allows you to
select the Ib measurement of a three-phase signal connected to the second input of
Scope2 block.

`Zoom on`

— Upper plot zoom

`Signal`

(default) | `FFT window`

Select `Signal`

to display the complete view of the signal
selected by the **Structure with time**, **Signal**,
and **Dimension** parameters in blue in the upper plot. The FFT window
that is specified by the **Start time**, **Number of
cycles**, and **Fundamental frequency** parameters is
displayed in red.

Select `FFT window`

to display only the portion of the
selected signal where the FFT analysis is performed in the upper plot.

`Start time (s)`

— Start time of the FFT analysis

0 (default) | positive scalar

Specifies the start times for the FFT analysis. The FFT analysis is performed on the portion of the signal starting at the specified time and for the specified number of cycles.

`Number of cycles`

—

1 (default) | positive integer

Specifies the number of cycles of the selected signal to analyze for the FFT analysis.

`Fundamental frequency (Hz)`

—

60 (default) | positive scalar

Specifies the fundamental frequency, in Hz, as a reference frequency for the FFT analysis.

`Max frequency (Hz)`

—

1000 (default) | positive scalar

Specifies the maximum frequency, in Hz, for the FFT analysis.

`Max frequency for THD computation`

—

`Nyquist frequency`

(default) | `Same as Max frequency`

Select `Nyquist frequency`

to compute the THD to the
maximum frequency equal to the Nyquist frequency. The Nyquist frequency is half the
sampling frequency of the selected signal.

Select `Same as Max frequency`

to compute the THD to the
maximum frequency equal to the frequency specified in the **Max frequency
(Hz)** parameter.

The THD calculation includes all the inter harmonics of the selected input signal.

`Display style`

— Display style for spectrum

`Bar (relative to fundamental)`

(default) | `Bar (relative to specified base) `

| `Bar (relative to DC component)`

| `List (relative to fundamental) `

| `List (relative to specified base)`

| `List (relative to DC component)`

Select `Bar (relative to fundamental)`

to display the
spectrum as a bar graph relative to the fundamental frequency. Select ```
Bar
(relative to specified base)
```

to display the spectrum as a bar graph
relative to the base defined by the **Base value** parameter. Select
`Bar (relative to DC component)`

to display the spectrum as a
bar graph relative to the DC component of the signal.

Select `List (relative to fundamental)`

to display the
spectrum as a list in percentages relative to the fundamental or DC component. Select
`List (relative to specified base)`

to display the spectrum
as a list in percentages relative to the base value defined by the **Base
value** parameter. Select ```
List (relative to DC
component)
```

to display the spectrum as a list relative to the DC
component of the signal.

`Base value`

— Harmonics base value

1 (default) | positive scalar

Enter a base value for the display of harmonics.

`Frequency axis `

— Frequency axis of FFT spectrum

`Hertz`

(default) | `Harmonic order`

Select `Hertz`

to display the spectrum frequency axis in
hertz. Select `Harmonic order`

to display the spectrum
frequency axis in harmonic order relative to the fundamental frequency.

`Compute FFT`

—

button

Displays the FFT analysis results for the selected simulation data signal in the
**FFT** graph.

## Version History

**Introduced in R2021a**