I IR and FIR Filter Design
Overview
For this project you will design and compare several types of IIR and FIR filters,
and examine how the designs vary with the input parameters.
You will also be
comparing the designs possible with IIR and FIR methods.
Since these methods are
traditionally specified differently you should review the contents of the
Matlab
Ripple
Project before continuing.
Commands you may find useful in this project
include
subplot, orient tall, orient landscape, and print
.
IIR Filter Design
1.
Analyze a SixthOrder Digital Butterworth Lowpass I IR
Filter.
Use the
M
ATLAB
command butter to design a sixthorder
lowpass IIR filter with cutoff frequency
ϖ
c
= 0.33
π
. (Note that the
Wn
parameter in
butter
corresponds to a normalized frequency so
that for this
filter,
Wn = 0.33
.)
M
ATLAB
takes care of the analog filter
design and uses the bilinear transformation to transform the analog
filter into a digital filter. Plot the magnitude and phase frequency
responses, the pole/zero plot for the system, and the first 20 values
of the impulse response of the system.
2.
Analyze a SixthOrder Digital Chebyshev Lowpass I IR Filter
.
Use the
M
ATLAB
command
cheby1
to design a sixthorder lowpass IIR
filter with a cutoff frequency
ϖ
c
= 0.33
π
and passband ripple of 0.5
dB. Plot the magnitude and phase frequency responses, the
pole/zero plot for the system, and the first 20 values of the impulse
response of the system.
f2000c
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3.
Analyze a SixthOrder Digital Elliptic Lowpass I IR Filter.
Use
the
M
ATLAB
command
ellip
to design a sixthorder lowpass IIR filter
with a cutoff frequency
ϖ
c
= 0.33
π
, passband ripple of 0.5 dB, and
stopband ripple that is 30 dB less than the passband response. Plot
the magnitude and phase frequency responses, the pole/zero plot for
the system, and the first 20 values of the impulse response of the
system.
4.
Compare the Order of the Three Filter Design Methods.
Consider a digital filter specification for an IIR lowpass filter with
passband cutoff frequency
ϖ
p
= 0.45
π
, stopband cutoff frequency
ϖ
s
= 0.5
π
, passband ripple of 0.1 dB, and stopband attenuation below
40 dB. What order digital Butterworth, Chebyshev, and Elliptic
lowpass IIR filters will meet these specifications? Use the
buttord
,
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 Fall '05
 HEMAMI
 Digital Signal Processing, Signal Processing, ZOOM, passband edge

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