ST_CM_ZoomFFT_InitPars

Function block-specific structure with initialization parameters, which are analyzed when the function block is initialized.

TYPE ST_CM_ZoomFFT_InitPars EXTENDS ST_CM_Object_InitPars :
STRUCT
    nFFT_Length       : UDINT := 2048;       (* Length of FFT. *)
    fSampleRate       : LREAL := 10000.0;    (* Sample rate in Hertz. *)
    fCenter           : LREAL := 200.0;      (* Center frequency of band in Hertz. *)
    nDecimationFactor : UDINT := 16;         (* FFT decimation factor. *)
    nOrder            : UDINT := 4;          (* Order of lowpass filter in range [1 .. 20]. *)
    nChannels         : UDINT := 1;          (* Number of channels. *)
END_STRUCT
END_TYPE

• nFFT_Length is the length of the FFT. It must be greater than one and an integral power of two.
• fSampleRate Sampling rate of the incoming time signal. The value is used for the scaling of the result in Hz.
• fCenter is the center of the frequency band to be used. The bandwidth depends on the decimation factor.
• nDecimationFactor is the decimation factor of the applied low-pass filter after centering the input signal. The value must be a power of two to ensure integer division when downsampling.
• nOrder defines the order of the IIR filter used.
• nChannels defines the number of independent channels. This must be greater than zero.