Second-order IIR peak or resonator filter
Design and plot an IIR peaking filter that boosts the frequency at 1.75 KHz in a signal and has a bandwidth of 500 Hz at the -3 dB point.
fs = 10000; wo = 1750/(fs/2); bw = 500/(fs/2); [b,a] = iirpeak(wo,bw); fvtool(b,a)
The peak filter has the desired gain and bandwidth at 1.75 KHz.
w0— Peak frequency
Peak frequency of the IIR filter, specified as a positive scalar in the range
(0.0,1.0), where 1.0 corresponds to π radians per sample in the
bw— Bandwidth of filter
Bandwidth of the filter at a level of +
ab decibels, specified
as a positive scalar in the range
The quality factor (Q factor) q for the filter is related to the filter bandwidth by q = ω0 / bw where ω0 is the signal frequency to boost.
ab— Magnitude response at filter bandwidth
3(default) | scalar
Magnitude response at the filter bandwidth
bw, specified as a
scalar in dB. Including the optional input argument
ab lets you
specify the magnitude response bandwidth at a level that is not the default
+3 dB point, such as
+6 dB or
num— Numerator coefficients
Numerator coefficients of the second order IIR peak filter transfer function, returned as a real-valued three-element row vector.
den— Denominator coefficients
Denominator coefficients of the second order IIR peak filter transfer function, returned as a real-valued three-element row vector.
 S.J.Orfanidis. Introduction To Signal Processing. Englewood Cliffs, New Jersey: Prentice-Hall, 1996.
Usage notes and limitations:
All inputs must be constant. Expressions or variables are allowed if their values do not change.