IIR Filter Design Using MATLAB

I. IIR Filter Order Selection
※ IIR Filter는 Filter 차수를 임의로 정하는 것이 아니라 Filter의 Spec에 따라 최적의 Filter 차수를 결정하여 사용해야 한다.

1. buttord

- Butterworth Filter order selection
▶ 기본 형태
[n,wn] = buttord(wp, ws, Rp, Rs)
n : IIR Filter order
wn : Normalized Cutoff Frequency (where, 1 corresponds to radians/sample)
wp : Normalized Passband Edge Frequency (where, 1 corresponds to radians/sample)
ws : Normalized Stopband Edge Frequency (where, 1 corresponds to radians/sample)
Rp : Passband Ripple (Rp dB)
Rs : Stopband Attenuation (Rs dB)
For example,
Lowpass : wp = 0.1, ws = 0.2
Highpass : wp = 0.2, ws = 0.1
Bandpass : wp = [0.2 0.7], ws = [0.1 0.8]
Bandstop : wp = [0.1 0.8], ws = [0.2 0.7]

2. Cheb1ord / Cheb2ord

- Chebyshev Filter Type I / Type II order selection
▶ 기본 형태
[n,wn] = cheb1ord(w…(생략)