Which of the following cannot be the Fourier series expansion of a periodic sign

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Question
Which of the following cannot be the Fourier series expansion of a periodic signal?
Options
A. x(t) = 2 cos t + 3 cos 3t
B. x(t) = 2 cos pt + 7 cos t
C. x(t) = cos t + 0.5
D. x(t) = 2 cos 1.5pt + sin 3.5 pt

Correct Answer

x(t) = cos t + 0.5

Explanation

x(t) = cos t + 0.5

not satisfies the Dirichlet condition.

The integration of constant term is ?.

Communication Systems problems

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1. If C is capacity of noisy channel, (bits/s), ?f is bandwidth Hz and S/N is signal to noise ratio, then
Options
A.
B.
C.
D.

2. A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output?
Options
A. 1002 kHz
B. 1000 kHz
C. 999.2 kHz
D. 998.0 kHz

3. Tracking of extra terrestrial objects requires
Options
A. high transmitting power
B. very sensitive receiver
C. fully steerable antenna
D. all of the above

6. In colour TV receiver, varactor diode is used for
Options
A. detection
B. rectification
C. tuning
D. both (a) and (b)

7. Frequency shift keying is used mostly in
Options
A. telegraphy
B. telephony
C. satellite communication
D. radio transmission

8. Which of the following has the highest input impedance?
Options
A. CE
B. CB
C. CC
D. Push pull

9. Degaussing in a picture tube means
Options
A. Adding magnetism in mask and mounting frame
B. Removing residual magnetism in mask, shield etc...
C. Increasing resistance of coils to decrease time constant
D. Decreasing resistance of coils to increase time constant.

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