Sliding DFT

Block diagram

Program parameters

The table below shows a list of the important parameters for configuring the function blocks.

Explanations

The scope project included in the sample visualizes the calculated spectra over their magnitude in the range of 0 to 1 kHz. On the one hand, the influence of the side lobes in the spectrum of the function block FB_CMA_SlidingDFT (blue line) is noticeable. The deviations essentially depend on the chosen damping parameter fDampingFactor. The deviations become smaller with values above 0.995, but the calculation becomes unstable with too little attenuation (>0.999). Due to the definition of the recursion rule for the spectral line k = 0, the calculation for the DC component, on the other hand, is more accurate. An improvement of the calculated values can be achieved by applying the Hanning window in the spectral range (fig. below).

A significant difference between the two function blocks is the utilization in the respective task. This is illustrated in the following graphic.

In contrast to the utilization peaks of the RealFFT (fig. below), the utilization of the SDFT (fig. above) is more constant. The latter value is significantly higher on average, but is subject to fewer fluctuations.

Requirements