Lecture #9 - IIR Filter Design Methods

Question 1

Compare between FIR and IIR filters on the property of: h[n]

Answer 1

FIR; finite
IIR; infinite

Question 2

Compare between FIR and IIR filters on the property of: stability

Answer 2

FIR; inherently stable - all zeros

IIR; depends on poles

Question 3

Compare between FIR and IIR filters on the property of: output

Answer 3

FIR; convolution

IIR; recursion

Question 4

Compare between FIR and IIR filters on the property of: phase

Answer 4

FIR; can have linear phase

IIR; difficult to control phase-distortion

Question 5

Compare between FIR and IIR filters on the property of: No. of Coefficients

Answer 5

FIR; requires more coefficients

IIR; fewer coefficients - faster, less memory

Question 6

Compare between FIR and IIR filters on the property of: causality

Answer 6

FIR; can be made causal

IIR; usually non-causal

Question 7

Give the characteristics of a butterworth filter

Answer 7

1. In terms of frequency response, there are no ripples in the passband and the stopband - maximally flat filter
2. Smooth, monotonically decreasing frequency response in the transition region.

Question 8

Give the characteristics of a chebyshev filter

Answer 8

1. Narrower transition range than the BW filter for same filter - passband with more ripples
2. Equiripple magnitude response in passband, monotonically decreasing magnitude response in the stopband, and sharper roll-off in the transition region
3. Best approximation to the ideal response of any filter for a specified order and ripple

Question 9

Give the characteristics of an eliptic filter

Answer 9

1. Equiripple in both passband and stopband
2. For same filter order, fastest transition in gain between the passband and the
   stopband

Question 10

Give the characteristics of a bessel filter

Answer 10

1. similar frequency response to the Butterworth - smooth in the passband and in the stopband.
2. For same filter order, stopband attenuation much lower than Butterworth.
3. Of all filter types, has the widest transition range if filter order is fixed.

Question 11

Name two design methods for digital filters

Answer 11

1. Impulse invariance
2. Bilinear transformation