DFT Signal Analysis

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

1. If the signal to be analyzed is an analog signal, we would pass it through an anti-aliasing filter with B as the bandwidth of the filtered signal and then the signal is sampled at a rate __________
a) Fs ≤ 2B
b) Fs ≤ B
c) Fs ≥ 2B
d) Fs = 2B

2. What is the highest frequency that is contained in the sampled signal?
a) 2Fs
b) Fs/2
c) Fs
d) None of the mentioned

3. The finite observation interval for the signal places a limit on the frequency resolution.
a) True
b) False

4. If {x(n)} is the signal to be analyzed, limiting the duration of the sequence to L samples, in the interval 0≤ n≤ L-1, is equivalent to multiplying {x(n)} by?
a) Kaiser window
b) Hamming window
c) Hanning window
d) Rectangular window

5. What is the Fourier transform of rectangular window of length L?
a) sin(ωL2)sin(ω2)ejω(L+1)/2
b) sin(ωL2)sin(ω2)ejω(L−1)/2
c) sin(ωL2)sin(ω2)e−jω(L−1)/2
d) None of the mentioned

6. If x(n)=cosω0n and W(ω) is the Fourier transform of the rectangular signal w(n), then what is the Fourier transform of the signal x(n).w(n)?
a) 1/2[W(ω-ω0)- W(ω+ω0)]
b) 1/2[W(ω-ω0)+ W(ω+ω0)]
c) [W(ω-ω0)+ W(ω+ω0)]
d) [W(ω-ω0)- W(ω+ω0)]

7. The characteristic of windowing the signal called “Leakage” is the power that is leaked out into the entire frequency range.
a) True
b) False

8. Which of the following is the advantage of Hanning window over rectangular window?
a) More side lobes
b) Less side lobes
c) More width of main lobe
d) None of the mentioned

9. Which of the following is the disadvantage of Hanning window over rectangular window?
a) More side lobes
b) Less side lobes
c) More width of main lobe
d) None of the mentioned

10. The condition with less number of samples L should be avoided.
a) True
b) False

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