# 2.11.1.3 ifft1

Analysis: Signal Processing: FFT: IFFT

## Brief Information

Compute inverse fourier transform

## Command Line Usage

 

1. ifft1 ix:=Col(2); 

2. ifft1 ix:=(Col(2),Col(3)); 

3. ifft1 ix:=Col(2) win:=hanning correct:=power; 

4. ifft1 ix:=Col(2) unwrap:=1; 

5. ifft1 ix:=Col(2) plot:=amp; 

## Variables

Display
Name
Variable
Name
I/O
and
Type
Default
Value
Description
Input ix

Input

vector<complex>

<active>

Specifies the input signal, which could be complex. The real and imaginary parts of the signal can be saved in two different columns or in a single column. The default is <Active>, which corresponds to the active dataset.

Sampling Interval interval

Input

double

1

Specifies the sampling interval. The default is <Auto>, which corresponds to automatically-computed interval. Please see the Algorithm section for more details.

Plot plot

Input

int

ap

Specifies what will be plotted in the preview window and outputted to the result graph sheet.

Option list

• 0=none:None
None
• 1=ap:Amplitude /Phase
The amplitude and phase of the result
• 2=real:Real
The real parts of the result data points
• 3=img:Imaginary
The imaginary parts of the result data points
• 4=amp:Amplitude
The amplitudes of the result
• 5=phase:Phase
The phase of the result
Undo Shift Input Data shift

Input

int

1

Specifies whether the input is generated by a FFT with the results shifted. If this option is checked, the input data points will first be swapped in order to undo the effect of shifting.

Window win

Input

int

Hamming

Specifies the window function used to suppress the leakage. Please see the algorithm section for further details of these window types.

Option list

• 0=rect:Rectangle
Rectangular window
• 1=welch:Welch
Welch window
• 2=tri:Triangular
Triangular window
• 3=bartlett:Bartlett
Bartlett window
• 4=hanning:Hanning
Hanning window
• 5=hamming:Hamming
Hamming window
• 6=blackman:Blackman
Blackman window
• 7=gauss:Gaussian
Gaussian window
• 8=kaiser:Kaiser
Kaiser window
Alpha alpha

Input

double

0

This variable is only available when window type is Gaussian. It specifies the Alpha parameter (the reciprocal of the standard deviation) for Gaussian window.

Beta beta

Input

double

0

This variable is only available when window type is Kaiser. It specifies the Beta parameter for Kaiser window.

Window Correction correct

Input

int

amplitude

Specifies the Window Correction Factor used to correct the alteration made by applying a window to the input data.

Option list

• none:None
No correction is applied.
• amp:Amplitude
Amplitude Correction is applied.
• power:Power
Energy Correction is applied.
Factor factor

Input

int

ee

Specifies whether the Electrical Engineering or Science convention is used to set the sign of the exponential phase factor.

Option list

• ee :-1 (Electrical Engineering)
The phase factor sign will be the opposite of the Science option.
• science:+1 (Science)
The phase factor will be set according to the formulae listed in page 503 of Numerical Recipes in C, 2nd edition
Unwrap Phase unwrap

Input

int

1

Specifies whether the phase should be unwrapped. If wrapped, phase data will be defined in the range of -180° to +180°

Result Data Sheet rd

Output

ReportData

[<input>]<new>

Specifies the output data sheet.

Result Graph Sheet rt

Output

ReportTree

[<input>]<new template:=graph>

Specifies the output graph sheet.

## Examples

1. To perform an inverse Fourier transform using default settings on complex data whose real parts and imaginary parts are in columns 2 and 3 respectively, use the script command:

ifft1 ix:=(Col(2), Col(3))

2. To perform an inverse Fourier transform on data using a pre-saved smoothing theme file, save your preferences in the advanced options in the ifft1 dialog. Execute it by typing the following script command, using your own saved-theme title:

ifft1 -t "my ifft1 theme.oth"