2.11.1.3 ifft1

Contents

Menu Information

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;

X-Function Execution Options

Please refer to the page for additional option switches when accessing the x-function from script

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"

More Information

For more information, please refer to our User Guide.


Related X-Functions

fft1, fft2, ifft2

Keywords:discrete, amplitude, phase, power, window correction