SIMPLORER User Manual V6.0 - FER-a

8
272 Using Signal Characteristics
FFT
>>Basics>Signal Characteristics>Special Waveform Parameters
The model provides the harmonic analysis of a signal, in the case the fundamental frequency
of the signal has to be known. The calculation is sine-based that means, a cosine signal would
have a phase shift of π/2.
The signal, which is to investigate, is created from the input signal by so-called windows. Because
of the multiplication with a window function all values outside of the window are '0'.
Only the active window is used for the calculation. The different window functions can be
considered as weighting factors for the signal within the window area.
Window function as Triangular, Von-Hann or Hamming should lower the leakage effect. In
this case the sub-harmonics are split to frequencies next to them. The effect occurs if the chosen
window range is not a integer of the multiples of the signal period. Not rectangular windows
affect adversely the amplitude response.
Dialog Settings
� «FFT Type»
In the list, select «Fixed» or «Flexible». Fixed means, only the first period (1/fundamental frequency
is considered. Flexible means, each period is calculated again.
«Delay [s]»
Defines the initial delay before the first period begins. Common parameter type. Enter a numerical
value, a variable, or an expression in the text box.
«Cut-off Frequency [Hz]»
Defines the Cut-off frequency of the FFT analysis. Only harmonic waves with the frequency
lower than the cut-off frequency are calculated. Common parameter type. Enter a numerical
value, a variable, or an expression in the text box. Please note: The specification of '0' means
there is no limitation.
«Amplitude Filter[%]»
Amplitudes smaller than the defined proportional value of the maximum are not displayed.
Common parameter type. Enter a numerical value, a variable, or an expression in the text box.
� «Window Type»
In the list, select the window «Rectangle», «Triangular», «Von-Hann», «Hamming», «Blackmann»,
«Lanzcos», or «Weber». Select the rectangular window if you want to investigate a
periodical signal.
«Fundamental Frequency [Hz]»
Defines the fundamental frequency of the FFT analysis. The frequency corresponds to 1/TPE-
RIO of the FFT model parameter. Common parameter type. Enter a numerical value, a variable,
or an expression in the text box.
«Input Signal»
Enter a quantity name used in your model sheet in the text box to define the input signal
(RLOAD.I, STEP.VAL, STATE.ST, VAR) or use the pin to connect a quantity. Please note: You
cannot use conservative nodes from circuits as input signal (N0002, GND).
� � «Use Pin»
If the box is checked, the input signal is defined by the quantity connected to the pin, otherwise
the value in the text box is used.