The singal analyzer app, preprocess the signal using these functions for the corresponding filters:
The filter specifications, decides the nature of filter that is selected (FIR or IIR). By default, the functions try to generate an FIR filter with minimum order. If the input signal length is less than or equal to the twice of minimum order, the filter chosen is IIR. In other words, if the minimum order is too large for input signal length, then, IIR filter is chosen.
Hope this helps.