GATE ECE topic:analog-communications PYQs & Answers

Questions 1–10 of 17. Imported answers require independent review unless marked reviewed.

Consider a real, narrowband signal

where the maximum frequency components of

and

are

and

, respectively. Which of the following statements is/are correct for

Your answerSelect all correct options. You can choose more than one.

represents a PSK modulated signal for suitable choices of

and

represents an amplitude modulated signal for suitable choices of

and

represents a band-limited Gaussian noise process.

never represents a narrowband FM signal.

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Consider a frequency-modulated (FM) signal

where

and

are, respectively, the amplitude and frequency (in Hz) of the carrier waveform. The frequency

is in Hz, and assume that

The peak frequency deviation of the FM signal in Hz is ______.

Your answerChoose one option.

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Consider a message signal

which is bandlimited to

, where

is in Hz. Consider the following two modulation schemes for the message signal:

• Double sideband-suppressed carrier (DSB-SC):

• Amplitude modulation (AM):

Here,

and

are the amplitude and frequency (in Hz) of the carrier, respectively. In the case of AM,

denotes the modulation index.

Consider the following statements: (i) An envelope detector can be used for demodulation in the DSB-SC scheme if

for all

. (ii) An envelope detector can be used for demodulation in the AM scheme only if

for all

Which of the following options is/are correct?

Your answerSelect all correct options. You can choose more than one.

(i) is TRUE

(i) is FALSE

(ii) is TRUE

(ii) is FALSE

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An amplitude modulator has output (in Volts)

The carrier power normalized to 1

resistance is 50 Watts. The ratio of the total sideband power to the total power is 1/9. The value of

(in Volts, rounded off to two decimal places) is ______ .

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Let a frequency modulated (FM) signal

, where

is a message signal of bandwidth

. It is passed through a non-linear system with output

. Let

denote the FM bandwidth. The minimum value of

required to recover

from

Your answerChoose one option.

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Consider an FM broadcast that employs the pre-emphasis filter with frequency response

where

rad/sec. For the network shown in the figure to act as a corresponding de-emphasis filter, the appropriate pair(s) of

values is/are ______.

Diagram for Electronics and Communication Engineering question 51

Your answerSelect all correct options. You can choose more than one.

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Consider a carrier signal which is amplitude modulated by a single-tone sinusoidal message signal with a modulation index of 50%. If the carrier and one of the sidebands are suppressed in the modulated signal, the percentage of power saved (rounded off to one decimal place) is ______.

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A sinusoidal message signal having root mean square value of 4 V and frequency of 1 kHz is fed to a phase modulator with phase deviation constant 2 rad/volt. If the carrier signal is

, the maximum instantaneous frequency of the phase modulated signal (rounded off to one decimal place) is ____ Hz.

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Consider a superheterodyne receiver tuned to 600 kHz. If the local oscillator feeds a 1000 kHz signal to the mixer, the image frequency (in integer) is _____ kHz.

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For the modulated signal x(t) = m(t) cos(2πf_c t), the message signal m(t) = 4 cos(1000πt) and the carrier frequency f_c is 1 MHz. The signal x(t) is passed through a demodulator, as shown in the figure below. The output y(t) of the demodulator is

Diagram for Electronics and Communication Engineering question 42

Your answerChoose one option.

cos(46πt).

cos(92πt).

cos(1000πt).

cos(540πt).

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GATE ECE topic:analog-communications PYQs

How to practice topic:analog-communications

Question 57

Question 14

Question 28

Question 28

Question 45

Question 51

Question 22

Question 49

Question 50

Question 42