2.11.1.3 ifft1
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
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Variable Name
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I/O and Type
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Default Value
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Description
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Input
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ix
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Input
vector<complex>
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<active>
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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.
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Sampling Interval
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interval
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Input
double
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1
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Specifies the sampling interval. The default is <Auto>, which corresponds to automatically-computed interval. Please see the Algorithm section for more details.
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Plot
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plot
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Input
int
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ap
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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
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Undo Shift Input Data
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shift
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Input
int
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1
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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.
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Window
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win
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Input
int
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Hamming
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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
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Alpha
|
alpha
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Input
double
|
0
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This variable is only available when window type is Gaussian. It specifies the Alpha parameter (the reciprocal of the standard deviation) for Gaussian window.
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Beta
|
beta
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Input
double
|
0
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This variable is only available when window type is Kaiser. It specifies the Beta parameter for Kaiser window.
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Window Correction
|
correct
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Input
int
|
amplitude
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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
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Input
int
|
ee
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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
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Unwrap Phase
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unwrap
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Input
int
|
1
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Specifies whether the phase should be unwrapped. If wrapped, phase data will be defined in the range of -180° to +180°
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Result Data Sheet
|
rd
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Output
ReportData
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[<input>]<new>
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Specifies the output data sheet.
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Result Graph Sheet
|
rt
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Output
ReportTree
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[<input>]<new template:=graph>
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Specifies the output graph sheet.
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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
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