Online Electronics and Communication Engineering Test - Previous Exam Papers Test 2

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Total number of questions: 20.
Time allotted: 30 minutes.
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In a radar system, the range of R₁ is achieved at a frequency f₁. Then the range R₂ at frequency R₂ = 8f₁ would be __________ [Neglect effect of 1 on the Beam width.]

R₂ = R₁

R₂ = 4R₁

R₂ = 2

R₁

R₂ =

[#]

Find Y- parameters

None of these

[#]

Power gain of antenna equals directive gain in VHF and UHF range if and only if efficiency of the antenna is __________ .

0.25

0.5

0.75

[#]

For the given phase lead network, the maximum possible phase lead is

sin^-1

30°

45°

60°

[#]

Time domain equivalent circuit of the figure is

None of the above

[#]

The region between a pin of parallel perfectly conducting planes of infinite extent is y and z directions is partially filled with a dielectric as shown below.

A 30 GHz TE₁₀ wave is incident on the air-dielectric interface. The VSWR at the interface is

- 2

[#]

A transmitted using AM has in modulated carrier output power of 10 KW and can be modulated to a maximum depth of 90% by a sinusoidal modulating voltage without causing overloading. Find the value to which an modulated carrier power can be increased without resulting in overloading if the maximum permitted modulating index is 40%

14 KW

12.96 KW

26.96 KW

2.96 KW

[#]

A signal with ± 10 V ranged and 1 KHz band width is being digitized using a sample and hold circuit and a 10 bit quantizer. The quantization step is :

1 x 10^-9 V

5 x 10^-9 V

2.5 x 10^-9 V

0.5 x 10^-9 V

[#]

The circuit I in figure is

1 mA

4 mA

8 mA

10 mA

[#]

10.

The equivalent form of the logical expression (ABC + ABC + ABC + ABC + ABC) is:

C + (A ⊕ B)

(A + B + C)(A + B + C)

(A + B + C)(A + B + C)(A + B + C)

[#]

11.

For a binary symmetric channel, the error probability P_c(0) = P_c(1) =

and errors are statistically independent. The channel capacity for a signalling speed 2 bits/second.

2 bits/sec

1.69 bits/sec

4 bits/sec

1 bit/sec

[#]

12.

Which of the following statements about the matched filter in a communication receiver are correct?

Its impulse response depends on the signed shape
It maximizes the SNR at the detection shape.
It produces ISI.
It may produce phase error if synchronization is improper.

Select the correct answer from the codes given below:

1 and 4 only

1 and 2 only

2, 3 and 4

1, 2 and 4

[#]

13.

The output of a Mealy system is 1 if there has been a pattern of 11000, otherwise 0. The minimum state for this system is :

[#]

14.

Consider the following circuit using an ideal OP-AMP. The I-V characteristics of the diode is described by the relation

where V_T = 25mV, I₀ = 1mA and V is the voltage across the diode (taken as positive for forward bias). For an input voltage V₁ = - 1 V, the output voltage V₀ is

0 V

0.1 V

0.7 V

1.1 V

[#]

15.

What is the purpose of DMA facility in microprocessor based system?

To increase the speed of data transfer between the mP and the I/O devices

To increase the speed of data transfer between the mP and the memory

To increase the speed of data transfer between the memory and the I/O devices

To improve the reliability of the system

[#]

16.

An 8085 executes the following instructions


2710 LXI H, 30A0H
2713 DAD H
2714 PCHL

All addresses and constants are in Hex. Let PC be the contents of the program counter and HL be the contents of the HL register pair just after executing PCHL.
Which of the following statements is correct?

PC = 2715 H HL = 30A0 H

PC = 30A0H HL = 2715H

PC = 6104 H HL = 6140 H

PC = 6140H HL = 2715H

[#]

17.

The spectral range of a band pass signal extends from 10 MHz to 10.4 MHz. What is the minimum sampling frequency required for reconstruction?

20 MHz

20.8 MHz

20.4 MHz

0.8 MHz

[#]

18.

The maximum positive and negative numbers which can be represented in 2's complement form using n bits are respectively

+(2^{n + 1} - 1), - (2^{n - 1} - 1)

+(2^{n + 1} - 1), - 2^{n - 1}

+2^{n - 1}, - 2^{n - 1}

+2^{n + 1}, - (2^{n - 1} + 1)

[#]

19.

The Nyquist plot of a stable, transfer function G(s) is shown in the figure. We are interested in the stability of the closed loop system in the feedback configuration shown.

Which of the following statements is true?

G(s) is an all-pass filter

G(s) has a zero in the right-half plane

G(s) is the impedance of a passive network

G(s) is marginally stable

[#]

20.

Which of the following are universal gates?

NAND
NOR
XOR

Select the correct answer from the codes given below:

1 and 2 only

1 and 3 only

2 and 3 only

1, 2 and 3

[#]

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