Electronics and Communication Engineering (ECE) Exam  >  Electronics and Communication Engineering (ECE) Questions  >  Which of the following cannot be the Fourier ... Start Learning for Free
Which of the following cannot be the Fourier series expansion of a periodic signal?
  • a)
    x(t) = 2 cos t + 3 cos 3t
  • b)
    x(t) = 2 cos
    p
    t + 7 cos t
  • c)
    x(t) = cos t + 0.5
  • d)
    x(t) = 2 cos 1.5
    p
    t + sin 3.5
    p
    t
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
Which of the following cannot be the Fourier series expansion of a per...
x(t) = cos t + 0.5
not satisfies the Dirichlet condition.
The integration of constant term is ∞.
View all questions of this test
Most Upvoted Answer
Which of the following cannot be the Fourier series expansion of a per...
Fourier Series Expansion

The Fourier series expansion is used to represent a periodic signal as a sum of harmonically related sinusoids. It is given by the equation:

x(t) = a0 + ∑(n=1 to infinity) (an cos(nω0t) + bn sin(nω0t))

where a0, an, and bn are the Fourier coefficients, ω0 is the fundamental frequency, and t is time.

Cannot be the Fourier series expansion

Option C, x(t) = cos(t) + 0.5, cannot be the Fourier series expansion of a periodic signal because it contains a constant term (0.5) which does not oscillate with time. The Fourier series expansion represents a periodic signal as a sum of harmonically related sinusoids, and therefore, should not have a constant term.

Other Options

Option A, x(t) = 2 cos(t) + 3 cos(3t), can be represented as the Fourier series expansion:

x(t) = 2 cos(t) + 3/2 cos(2t) - 1/2 cos(4t)

Option B, x(t) = 2 cos(pt) + 7 cos(t), can be represented as the Fourier series expansion:

x(t) = 2 cos(pt) + 7/2 cos(2t) - 3/2 cos(3t) + 1/2 cos(4t) - 1/2 cos(5t) + ...

Option D, x(t) = 2 cos(1.5pt) + sin(3.5pt), can be represented as the Fourier series expansion:

x(t) = √5 cos(0.5t - θ)

where θ = arctan(7/3) and the Fourier coefficients are given by:

a0 = 0
an = (-1)n+1 √5/(nπ) sin(nθ) for n = 1, 2, 3, ...
bn = (-1)n+1 √5/(nπ) cos(nθ) for n = 1, 2, 3, ...

Conclusion

Option C cannot be the Fourier series expansion of a periodic signal because it contains a constant term, which violates the condition of representing a periodic signal as a sum of harmonically related sinusoids.
Free Test
Community Answer
Which of the following cannot be the Fourier series expansion of a per...
B

for fourier series to be possible signal should be periodic.

Here when you calculate periodicity of signal you will get irrational (T1/T2). Therefore non periodic.
Attention Electronics and Communication Engineering (ECE) Students!
To make sure you are not studying endlessly, EduRev has designed Electronics and Communication Engineering (ECE) study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Electronics and Communication Engineering (ECE).
Explore Courses for Electronics and Communication Engineering (ECE) exam

Similar Electronics and Communication Engineering (ECE) Doubts

Top Courses for Electronics and Communication Engineering (ECE)

Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer?
Question Description
Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Question and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus. Information about Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer?.
Solutions for Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for Electronics and Communication Engineering (ECE). Download more important topics, notes, lectures and mock test series for Electronics and Communication Engineering (ECE) Exam by signing up for free.
Here you can find the meaning of Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer?, a detailed solution for Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? has been provided alongside types of Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice Which of the following cannot be the Fourier series expansion of a periodic signal?a)x(t) = 2 cos t + 3 cos 3tb)x(t) = 2 cos pt + 7 cos tc)x(t) = cos t + 0.5d)x(t) = 2 cos 1.5pt + sin 3.5 ptCorrect answer is option 'C'. Can you explain this answer? tests, examples and also practice Electronics and Communication Engineering (ECE) tests.
Explore Courses for Electronics and Communication Engineering (ECE) exam

Top Courses for Electronics and Communication Engineering (ECE)

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev