4th order IIR filter

On the left, z-domain representation graphed from -2:2, -2i:2i. Green represents values of magnitude 1.0, with higher magnitudes moving toward red/white (red = 2.0) and lower values moving toward violet.

On the right, the frequency response of the filter. Freq on x from 0 to nyquist, amplitudes on y from 0:2

Modify the coefficients directly with the sliders below

Or, you can click on the plots themselves. Clicking on the frequency response will create a notch or peaking filter at the clicked frequency and amplitude. Successive clicks on the z-domain plot will place a pole, then a zero, then replace the pole, then the zero, etc.

bandwidth