Digital Signal Processing Reference
In-Depth Information
d. We wish to use the Kaiser window method to design a digital band-
pass filter satisfying the following specification:
()
<
−<
002
.
He
j
ω
002
.
,
0
≤
ωπ
≤
0.2
()
<
j
ω
095
.
<
He
105
.
,
0.3
πω
≤≤
07
.
π
()
<
He
j
ω
−
0 001
.
<
0 001
.
,
0.75
πωπ
≤
≤
The filter will be designed by applying bilinear transform with
T
= 5 ms
to a prototype continuous-time filter. State the specifications that should be
used to design a prototype continuous-time filter.
5.3
Computer Laboratory: Design of FIR and IIR Digital
Filters Using Computer Aided Design (CAD) Techniques
This section explains how computer software, such as MATLAB,
4
can be
used to design and implement FIR and IIR digital filters. Try out each of the
commands given below and familiarize yourself with the types of MATLAB
commands and formats.
5.3.1
Basic MATLAB Commands to Calculate and Visualize Complex
Frequency Response
The difference equation of a general digital filter can be written as:
ayn
()
+
ayn
(
−
1
)
+ … −
a yn N
(
)
=
bxn
()
+
bxn
(
−
1
)
+ …
bbxn M
M
(
−
)
0
1
N
0
1
A compact MATLAB program is given below to plot the magnitude and
phase responses of the filter system, defined above by the difference equation.
% MATLAB Program to Plot Magnitude and Phase Response
of a Digital Filter
p = 100;
a = [a0 a1 … aN];
b = [b0 b1 … bM];
[H,w] = freqz(b,a,p) ;returns the p-point complex
frequency response.
subplot(2,1,1)
plot(w,abs(H))
; plots the magnitude response
subplot(2,1,2)
plot(w,angle(H))
; plots the phase response
