SASLab Manual
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Main window : Analyze > Specials > Pulse Train Analysis > Settings > Spectral Analysis Setup
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This dilaog box defines the spectral analysis settings of the Pulse Train Analyis tool.
The FFT size determines the maximum duration of the analysis frame. The resulting Frame duration and the resulting Frequency resolution of the currently selected FFT size is displayed.
The weighting Window is applied to the analysis frame prior to calculating the FFT spectrum. Depending on the structure of the pulses, the specific window type may influence the peak frequency results. The Rectangle window will not influence the temporal structure (the location of the pulse within the analysis frame does not matter). The other weighting functions emphasize the middle of the analysis frame, which may distort the frequency spectrum. In case the pulses have a distinct start and end and the analysis frame fully covers the pulses, then the Rectangle window is recommended. In case the analysis frame is shorter than the pulse (pulses longer than the FFT size), then one of the other weighting functions will provide more reliable results.
The option limit the analysis frame to the detected pulse duration activates a zero-padding mode. If activated and if the pulse is shorter than the selected FFT size, then the FFT spectrum will be computed only from the detected pulse duration. Otherwise, the actual duration of the pulse is ignored and the spectrum is computed from the full (FFT size) frame that is centered on the detected pulse. This option does only have an effect as long as the durations of the pulses are determined (Gate function or Peak search with Hysteresis with the Duration activated). In case the duration is not available, spectrum will always be computed from the full FFT size.
In that case, it is also recommended to adjust the FFT size to the durations of the pulses.
The Bandwidth Settings define the threshold for the bandwidth calculation and the way how the bandwidth is determined. If the total option is activated, the bandwidth will cover all peaks that exceed the threshold. Otherwise, the bandwidth will only cover the maximum peak exceeding the threshold.
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