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1. A 2N-point DFT is applied on a 2N-point time-domain vector. The first N point

ID: 2249215 • Letter: 1

Question

1. A 2N-point DFT is applied on a 2N-point time-domain vector. The first N points in that vector consist of a

sampled sinewave with period M samples and N=iM. The last N samples are all set to zero. The sinusoid can be

resolved precisely by the DFT, i.e., only two frequency components out of the 2N are non-zero.

True

False

2. An N-point DFT is applied on a sampled sinewave with period M samples. The number of samples N is an

integer multiple of the period of the sinusoid, i.e., N=iM. The sinusoid can be resolved precisely by the N-point

DFT, i.e. only two frequency components out of the N are non-zero.

True

False

Explanation / Answer

a 2N-point DFT is applied on a 2N-point time-domain vector. The first N points in that vector consist of a sampled sinewave with period M samples and N=iM. The last N samples are all set to zero. The sinusoid can be
resolved precisely by the DFT, i.e., only two frequency components out of the 2N are non-zero.

it is true

An N-point DFT is applied on a sampled sinewave with period M samples. The number of samples N is an integer multiple of the period of the sinusoid, i.e., N=iM. The sinusoid can be resolved precisely by the N-point
DFT, i.e. only two frequency components out of the N are non-zero.

it is false