System object: dsp.IIRFilter
Package: dsp

Reset internal states of IIR filter




reset(H) resets the filter states of the IIR filter object, H, to their initial values of 0. The initial filter state values correspond to the initial conditions for the difference equation defining the filter. After the step method applies the IIR filter object to nonzero input data, the states may be nonzero. Invoking the step method again without first invoking thereset method may produce different outputs for an identical input.

For example:

H = dsp.IIRFilter;
[b,a] = ellip(20, 0.5, 80, 0.25);
H.Numerator = b;
H.Denominator = a;
n = 0:100;
x = cos(0.2*pi*n)+sin(0.8*pi*n);
y = step(H,x);
% Filter states are nonzero 
% Invoke step method again without resetting states
y1 = step(H,x);
isequal(y,y1) % returns 0
% Now reset filter states to 0
% Invoke step method 
y2 = step(H,x);
isequal(y,y2) % returns a 1

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