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Signal and systems miscellaneous

Signals and Systems

  1. The function x(t) is shown in the given figure. If X(jω) is the Fourier transform of the x(t), then |X(jω)| at ω = 0 will be—


    1. 0.5
    2. 1.5
    3. 2
    4. 3
Correct Option: D


Given waveform of x(t) is a combination of four shifted step function i.e.,

i.e.,  x(t) = ut +
1
+ ut +
1
- ut -
1
-u (t - 1).......A
222

F[x(t)] =
e
+
ejω/2
e−jω/2
e−jω

X(jω) =
ejω − jω/2
+
ejω/2 − e jω/2

X(jω) =
2
sin ω +
2
sin
ω
ωω2

|X(jω)|at ω = 0 = limω → 0
2
sin ω +
2
sin
ω
ωω2

= limω → 0
2.cos ω
+ 2 cos
ω
.
1
122

= 2 + 1 = 3.
Hence, alternative (D) is the correct choice.



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