This applet demonstrates the effect of applying an FIR digital filter to a sampled signal.
For an introductory tutorial on digital filters, see Digital Filters: An Introduction.
The input signal to the filter is generated in exactly the same way as for the spectrum analyser applet. Refer to the outline instructions for the FFT Spectrum Analyser applet for an explanation of the control panel settings.
The input signal, which is determined by the control panel settings, is plotted in the upper graph. The lower graph shows the output signal from the filter. The two graphs have the same vertical scale so the relative amplitudes of the input and output signals can be compared.
The applet allows any one of three FIR digital filters to be applied to the plotted signal:
Each of the three filters was designed by the window or "Fourier transform" method, using the Kaiser window function. The order of each filter is 34; the number of "taps" or product terms in the filter expression is thus 35.
Guidance notes are available to illustrate various aspects of digital filters using the applet.