# Impulse Invariance Filter Design

This set of Digital Signal Processing Questions for campus interviews focuses on “IIR Filter Design by Impulse Invariance”.

1. By impulse invariance method, the IIR filter will have a unit sample response h(n) that is the sampled version of the analog filter.
a) True
b) False

2. If a continuous time signal x(t) with spectrum X(F) is sampled at a rate Fs=1/T samples per second, the spectrum of the sampled signal is _____________
a) Non periodic repetition
b) Non periodic non-repetition
c) Periodic repetition
d) None of the mentioned

3. If a continuous time signal x(t) with spectrum X(F) is sampled at a rate Fs=1/T samples per second, then what is the scaled spectrum?
a) X(F)
b) Fs.X(F)
c) X(F)/Fs
d) None of the mentioned

4. When σ=0, then what is the condition on ‘r’?
a) 0<r<1
b) r=1
c) r>1
d) None of the mentioned

5. What is the equation for normalized frequency?
a) F/Fs
b) F.Fs
c) Fs/F
d) None of the mentioned

6. Aliasing occurs if the sampling rate Fs is more than twice the highest frequency contained in X(F).
a) True
b) False

7. Which of the filters have a frequency response as shown in the figure below?

a) Analog filter
b) Digital filter without aliasing
c) Digital filter with aliasing
d) None of the mentioned

8. The frequency response given in the above question is for a low pass digital filter.
a) True
b) False

9. Sampling interval T is selected sufficiently large to completely avoid or at least minimize the effects of aliasing.
a) True
b) False

10. Which of the following filters cannot be designed using impulse invariance method?
a) Low pass
b) Band pass
c) Low and band pass
d) High pass

11. Which of the following is the correct relation between ω and Ω?
a) Ω=ωT
b) T=Ωω
c) ω=ΩT
d) None of the mentioned

12. When σ<0, then what is the condition on ‘r’?
a) 0<r<1
b) r=1
c) r>1
d) None of the mentioned

13. When σ>0, then what is the condition on ‘r’?
a) 0<r<1
b) r=1
c) r>1
d) None of the mentioned

14. What is the period of the scaled spectrum Fs.X(F)?
a) 2Fs
b) Fs/2
c) 4Fs
d) Fs