GATE EC 2020 Set 1 — Question 39
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Signals & Systems → Discrete-Time Signals → DFT & FFT
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Question
A finite duration discrete-time signal is obtained by sampling the continuous-time signal at sampling instants . The 8-point discrete Fourier transform (DFT) of is defined asWhich one of the following statements is TRUE?
Correct answer
(C) Only X[2] and X[6] are non-zero.
Solution
The sampled signal is for . This can be written as . The 8-point DFT of a signal is . Here, and , and all other . Thus, and , while all other . Therefore, only and are non-zero.
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