Question

Design an analog elliptic lowpass IIR filter with specifications Fp=10 kHz., Ap=1 dB, Fs=15 kHz. And As=50 dB. Provide the following plots in MATLAB:

a. Magnitude

b. Log-magnitude

c. Group-delay

d. Impulse response

e. Pole-zero

Answer 1

Code:

clc;close all;clear all;

fp=10000; fs=15000;Ap=1;As=50;

Fs=40000;wp=2*fp/Fs; ws=2*fs/Fs;

%Elliptic Filter

[N,wp] = ellipord(wp,ws,Ap,As);

[b,a] = ellip(N,Ap,As,wp,'s');

w=0:pi/1000:pi;

[H,w]=freqs(b,a,w);

figure;

subplot(221)

n=0:1:20;

h=impz(b,a,21);

stem(n,h);grid;

xlabel('n')

ylabel('h(n)')

title('Impulse response')

subplot(222)

plot(w/pi,abs(H));grid;

xlabel('w/pi');ylabel('|H(w)|');

title('Magnitude response')

subplot(223)

plot(w/pi,20*log10(abs(H)));grid;

xlabel('w/pi');ylabel('|H(w)|');

title('Log Magnitude response')

gd=grpdelay(b,a,w);

subplot(224)

plot(w/pi,gd);grid;

xlabel('w/pi');ylabel('|H(w)|');

title('Group delay')

figure;

sys=tf(b,a);

pzplot(sys)