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What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?
  • a)
    {9,9,7,11}
  • b)
    {1,4,9,11,8,3}
  • c)
    {7,9,7,11}
  • d)
    {9,7,9,11}
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
What is the sequence y(n) that results from the use of four point DFTs...
Explanation: The four point DFT of h(n) is H(k)=1+2e-jkπ/2+3 e-jkπ (k=0,1,2,3)
Hence H(0)=6, H(1)=-2-j2, H(3)=2, H(4)=-2+j2
The four point DFT of x(n) is X(k)= 1+2e-jkπ/2+2 e-jkπ+3e-3jkπ/2(k=0,1,2,3)
Hence X(0)=6, X(1)=-1-j, X(2)=0, X(3)=-1+j
The product of these two four point DFTs is
Y ̂(0)=36, Y ̂(1)=j4, Y ̂(2)=0, Y ̂(3)=-j4
The four point IDFT yields y ̂(n)={9,7,9,11}
We can verify as follows
We know that from the previous question y(n)={1,4,9,11,8,3}
y ̂(0)=y(0)+y(4)=9
y ̂(1)=y(1)+y(5)=7
y ̂(2)=y(2)=9
y ̂(3)=y(3)=11.
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Most Upvoted Answer
What is the sequence y(n) that results from the use of four point DFTs...
Explanation:

  • Given impulse response, h(n) = {1, 2, 3} and input sequence, x(n) = {1, 2, 2, 1}

  • To find the sequence y(n) using 4-point DFTs, we need to calculate the DFT of h(n) and x(n) separately using the formula:


    • X(k) = Σx(n)exp(-j2πnk/N) where N is the size of DFT and k = 0, 1, 2, ..., N-1

    • H(k) = Σh(n)exp(-j2πnk/N) where N is the size of DFT and k = 0, 1, 2, ..., N-1


  • Using the above formula, we can calculate the DFT of x(n) and h(n) as follows:


    • X(0) = 1 + 2 + 2 + 1 = 6

    • X(1) = 1 + 2exp(-jπ/2) - 2 - 2exp(-jπ/2) = -2j

    • X(2) = 1 - 2 + 2 - 1 = 0

    • X(3) = 1 - 2exp(-jπ/2) - 2 + 2exp(-jπ/2) = 2j

    • H(0) = 1 + 2 + 3 = 6

    • H(1) = 1 + 2exp(-jπ/2) - 3 - 2exp(-jπ/2) = -1-j

    • H(2) = 1 - 2 + 3 = 2

    • H(3) = 1 - 2exp(-jπ/2) - 3 + 2exp(-jπ/2) = -1+j


  • Now, we can calculate the DFT of the output sequence y(n) using the formula:


    • Y(k) = X(k)H(k) where k = 0, 1, 2, ..., N-1


  • Using the above formula, we can calculate the DFT of y(n) as follows:


    • Y(0) = X(0)H(0) = 6*6 = 36

    • Y(1) = X(1)H(1) = (-2j)*(-1-j) = -2+2j

    • Y(2) = X(2)H(2) = 0*2 = 0

    • Y(3) = X(3)H(3) = (2j)*(-1+j) = -2-2
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What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?a){9,9,7,11}b){1,4,9,11,8,3}c){7,9,7,11}d){9,7,9,11}Correct answer is option 'D'. Can you explain this answer?
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What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?a){9,9,7,11}b){1,4,9,11,8,3}c){7,9,7,11}d){9,7,9,11}Correct answer is option 'D'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?a){9,9,7,11}b){1,4,9,11,8,3}c){7,9,7,11}d){9,7,9,11}Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?a){9,9,7,11}b){1,4,9,11,8,3}c){7,9,7,11}d){9,7,9,11}Correct answer is option 'D'. Can you explain this answer?.
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