FFT – Fast Fourier Transform

Block SymbolLicensing group: ADVANCED

Function Description
The function block FFT computes Fast Fourier Transform using the PocketFFT package [17]. The PocketFFT C99 implementation is based on FFTPack (in Fortran) [18], which is based on the chapter in [19].

Input data (a vector or a matrix) of the block are referenced by the uc input. If the input uc refers to a column vector (number of columns m = $1$ ) with the number of elements n, the FFT will be calculated from a single signal with n elements. If uc refers to a matrix with n rows and m columns, the FFT will be computed m times (once for each column).

Input data is processed according to the mode parameter (see below), which determines whether the calculation will be performed for real or complex data and forward or backward FFT. More precisely, one of the rfft_forward(), rfft_backward(), cfft_forward() or cfft_backward() functions of the PocketFFT package is called according to the mode parameter.

Output data are referenced by the uf input. The data has the same number of n rows and m columns as the data referenced by uc. If the uf input is connected to preallocated vector/matrix then the FFT algorithm output data are referenced by the yf output. If the uf input is not connected, the FFT is calculated in place and the output data is stored in the array referenced by the yc output and the original data referenced by uc is overwritten.

The uc reference is copied to the yc output, the uf reference is copied to the yf output.

The HLD input allows the user to temporarily stop the FFT calculation.

This block does not propagate the signal quality. More information can be found in the 1.4 section.

Input

uc	Input reference to input/output data	Reference
uf	Input reference to optional output data	Reference
HLD	Hold	Bool

Parameter

mode

FFT computation mode $⊙$ 1

Long (I32)

1 ....: Real forward
2 ....: Real backward
3 ....: Complex forward
4 ....: Complex backward

Output

yc	Output reference to input/output data	Reference
yf	Output reference to optional output data	Reference
E	Error indicator	Bool

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