InvFFTEx
Advanced Analysis Library Only
AnalysisLibErrType InvFFTEx (NIComplexNumber fft[], ssize_t numberOfElements, PFFTTable fftTable, int shifted, double timeDomainSignal[]);
Purpose
Computes the real inverse Fast Fourier Transform (FFT) of an input sequence.
National Instruments recommends you use this function instead of ReInvFFT. With InvFFTEx, you can use an FFT table. You also can compute a DC-centered inverse FFT.
To perform the same size FFT repeatedly, first use CreateFFTTable to create the FFT table and then pass the table to InvFFTEx to speed the computation. If you pass NULL for fftTable, the function creates the table internally and frees the table on exit.
The following code is the pseudocode for calling FFT routines:
N=1024; //Set length of signal tbl=CreateFFTTable(N); //Create N-point table for(;;){ Acquire_N_Point_Signal(signal); //Acquire N points FFT(signal,..., tbl,...); //Perform FFT or IFFT } DestroyFFTTable(tbl); //End, release FFT table resources
Parameters
| Input | ||
| Name | Type | Description |
| FFT | NIComplexNumber [] | The input frequency-domain sequence. |
| numberOfElements | ssize_t | The number of elements in fft. |
| FFTTable | PFFTTable | The FFT table created with CreateFFTTable. You can pass NULL for this parameter if you do not have a reusable FFT table. |
| shifted | int | Specifies whether fft is DC-centered. shifted must be one of the following values:
|
| Output | ||
| Name | Type | Description |
| timeDomainSignal | double [] | The real time-domain signal. |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 8.0 and later