Communication Systems - Study Mode

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[#131] An FM wave is represented by y(t) = 10sin[2000πt + 4sin1250πt]. The maximum frequency deviation is:

(A) 1250 Hz

(B) 2000 Hz

(C) 2500 Hz

(D) 4000 Hz

Correct Answer

(C) 2500 Hz

[#132] The amplitude modulated wave form s(t) = A C [1 + K a m(t)]cosω C t is used an ideal envelope detector. The maximum magnitude of K a m(t) is greater than 1. Which of the following could be the detector output?

(A) A C m(t)

(B) [$${ ext{A}}_{ ext{C}}^2$$ [1 + K a m(t)] 2

(C) [A C |1 + K a m(t)|]

(D) A C |1 + K a m(t)| 2

Correct Answer

(C) [A C |1 + K a m(t)|]

[#133] In an amplitude modulated system if the total power is 600 W and the power in the carrier is 400 W, the modulation index is

(A) 0.5

(B) 0.75

(C) 0.9

(D) 1

Correct Answer

(D) 1

[#134] An AM broadcast station operates at its maximum allowed total of 100 kW with 90% modulation. The power in the intelligence part is

(A) 28.8 kW

(B) 71.2 kW

(C) 35.6 kW

(D) 36.5 kW

Correct Answer

(A) 28.8 kW

[#135] A signal m(t) = 10cos 2π100t is frequency modulated. The resulting FM signal is x(t) = 20cos{2π10 6 t + 15sin(2π100t)}. The FM bandwidth is nearly

(A) 3.2 kHz

(B) 9.6 kHz

(C) 32 kHz

(D) 100 kHz

Correct Answer

(A) 3.2 kHz