ECE · all questions

Communication Systems
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Q61

A communication receiver has an intermediate frequency of 9 MHz. What is the frequency of its oscillator when it is tuned to 15 MHz?

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Q62

Which one of the statements regarding the following signal x(t) = 5sin(2π × 10³t)sin(2π × 10⁶t) is incorrect?

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Q63

The narrow band FM signal is 10cos(2π1000t + 0.2sin(2π100t)) what is instantaneous frequency:

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Q64

Match List-I with List-II and select the correct answer using the options given below:

List-I	List-II
a. Resistance	1. Current Noise
b. Diode	2. Partition Noise
c. Triode	3. Shot Noise
d. p-n junction Noise	4. Atmospheric
	5. Johnson Noise

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Q65

The advantages of DSB over SSB full carrier AM is

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Q66

Modems are used for data transmission telephone lines to

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Q67

Super heterodyne radio receiver suffers from-

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Q68

In the FM wave described by equation v = 15sin(4 × 10⁸t + 3sin1100t), the maximum frequency deviation is

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Q69

Probability density function of random variable x is:

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Q70

The auto-correlation function of a band limited (B) white noise process is given by

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Q71

The outputs of two noise sources each producing uniformly distributed noise over the range -a to +a are added. What is the p.d.f. of the added noise?

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Q72

In a FM demodulator,

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Q73

The power spectral density of the stationary noise process N(t) having auto correlation R_uu(τ) = Ke^-3|τ| is

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Q74

Noise figure is defined as

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Q75

The List-I and the list-II. Match the attribute to the modulation system that best meets it.

List-I (lists the attributes)	List-II (lists of the modulation systems)
a. Power efficient transmission of signals	1. Conventions AM
b. Most bandwidth efficient transmission of voice signals	2. FM
c. Simplest receiver structure	3. VSB
d. Bandwidth efficient transmission of signals with significant dc component	4. SSB-SC

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Q76

Noise in FM receiver is reduced by

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Q77

The most common detector used in an AM radio broadcast receiver is:

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Q78

A random process obeys Poisson's distribution. It is given that the mean of the process is 5. Then the variance of the process is

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Q79

For an AM signal, the bandwidth is 20 kHz and the highest frequency component present is 800 kHz. The carrier frequency used for this AM signal is

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Q80

Consider the following types of modulation
1. Amplitude modulation
2. Frequency modulation
3. Pulse modulation
4. Phase modulation
Which of the above modulation are used for telecasting TV programmes?

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