Frequency Transformations

Digital Communications Systems

This set of Digital Signal Processing Multiple Choice Questions & Answers (MCQs) focuses on “Frequency Transformations”.

1. What is the pass band edge frequency of an analog low pass normalized filter?
a) 0 rad/sec
b) 0.5 rad/sec
c) 1 rad/sec
d) 1.5 rad/sec

2. If H(s) is the transfer function of a analog low pass normalized filter and Ωu is the desired pass band edge frequency of new low pass filter, then which of the following transformation has to be performed?
a) s → s/Ωu
b) s → s.Ωu
c) s → Ωu/s
d) none of the mentioned

3. Which of the following is a low pass-to-high pass transformation?
a) s → s / Ωu
b) s → Ωu / s
c) s → Ωu.s
d) none of the mentioned

4. Which of the following is the backward design equation for a low pass-to-low pass transformation?
a) ΩS=ΩSΩu
b) ΩS=ΩuΩ′S
c) Ω′S=ΩSΩu
d) ΩS=Ω′SΩu

5. Which of the following is a low pass-to-band pass transformation?
a) s→s2+ΩuΩls(Ωu+Ωl)
b) s→s2−ΩuΩls(Ωu−Ωl)
c) s→s2+ΩuΩls(Ωu−Ωl)
d) s→s2−ΩuΩls(Ωu+Ωl)

6. Which of the following is the backward design equation for a low pass-to-high pass transformation?
a) ΩS=ΩSΩu
b) ΩS=ΩuΩ′S
c) Ω′S=ΩSΩu
d) ΩS=Ω′SΩu

7. Which of the following is a low pass-to-band stop transformation?
a) s→s(Ωu−Ωl)s2+ΩuΩl
b) s→s(Ωu+Ωl)s2+ΩuΩl
c) s→s(Ωu−Ωl)s2−ΩuΩl
d) none of the mentioned

8. If A=−Ω21+ΩuΩlΩ1(Ωu−Ωl) and B=Ω22−ΩuΩlΩ2(Ωu−Ωl), then which of the following is the backward design equation for a low pass-to-band pass transformation?
a) ΩS=|B|
b) ΩS=|A|
c) ΩS=Max{|A|,|B|}
d) ΩS=Min{|A|,|B|}

9. If A=Ω1(Ωu−Ωl)−Ω21+ΩuΩl and B=Ω2(Ωu−Ωl)Ω22−ΩuΩl, then which of the following is the backward design equation for a low pass-to-band stop transformation?
a) ΩS=Max{|A|,|B|}
b) ΩS=Min{|A|,|B|}
c) ΩS=|B|
d) ΩS=|A|

10. Which of the following is a low pass-to-high pass transformation?
a) s → s / Ωu
b) s → Ωu/s
c) s → Ωu.s
d) none of the mentioned

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