Electronics & Communication Gate Yearwise 

Electronics and Communication GATE 2017 Set-2 Questions with Answer

Ques 1 Analog Communication

The unmodulated carrier power in an AM transmitter is 5 kW. This carrier is modulated by a sinusoidal modulating signal. The maximum percentage of modulation is 50%. If it is reduced to 40%, then the maximum unmodulated carrier power (in kW) that can be used without overloading the transmitter is

5.21 is the correct answer.


Ques 2 Analog Communication

A modulating signal given by x(t)=5sin(4π103t-10πcos2π103t) V is fed to a phase modulator with phase deviation constant kp=5 rad/V. If the carrier frequency is 20 kHz, the instantaneous frequency (in kHz) at t=0.5 ms is

70 is the correct answer.


Ques 3 Control Systems

For the system shown in the figure, Y(s)/X(s)=

1 is the correct answer.


Ques 4 Control Systems

Consider the state space realization

The value of limt→∞|√(x12(t)+x22(t))| is

5 is the correct answer.


Ques 5 Control Systems

Which of the following statements is incorrect?

A

Lead compensator is used to reduce the settling time.

B

Lag compensator is used to reduce the steady state error.

C

Lead compensator may increase the order of a system.

D

Lag compensator always stabilizes an unstable system.


Ques 6 Control Systems

A unity feedback control system is characterized by the open-loop transfer function
G(s)=2(s+1)/(s3+ks2+2s+1).
The value of k for which the system oscillates at 2 rad/s is

0.75 is the correct answer.


Ques 7 Control Systems

A second-order LTI system is described by the following state equations.
d/dt x1(t)-x2(t)=0 and
d/dt x2(t)+2x1(t)+3x2(t)=r(t) where x1(t) and x2(t)
are the two state variables and r(t) denotes the input. The output c(t)=x1(t). The system is

A

undamped (oscillatory)

B

underdamped

C

critically damped

D

overdamped


Ques 8 Control Systems

A unity feedback control system is characterized by the open-loop transfer function
G(s)=10K(s+2)/(s3+3s2+10).
The Nyquist path and the corresponding Nyquist plot of G(s) are shown in the figures below.

If 0<K<1, then the number of poles of the closed-loop transfer function that lie in the right-half of the s-plane is

A

0

B

1

C

2

D

3


Ques 9 Digital Circuits

For the circuit shown in the figure. P and Q are the inputs and Y is the output.

The logic implemented by the circuit is

A

XNOR

B

XOR

C

NOR

D

OR


Ques 10 Digital Circuits

Consider the circuit shown in the figure.

The Boolean expression F implemented by the circuit is

A

X̄ȲZ̄+XY+ȲZ

B

X̄ȲZ̄+XZ+ȲZ

C

X̄ȲZ̄+XZ+ȲZ

D

X̄ȲZ̄+XZ+ȲZ


Ques 11 Digital Circuits

In a DRAM,

A

periodic refreshing is not required

B

information is stored in a capacitor

C

information is stored in a latch

D

both read and write operations can be performed simultaneously


Ques 12 Digital Circuits

The state diagram of a finite state machine (FSM) designed to detect an overlapping sequence of three bits is shown in the figure. The FSM has an input 'In' and an output 'Out'. The initial state of the FSM is S0.

If the input sequence is 10101101001101, starting with the left-most bit, then the number of times 'Out' will be 1 is

4 is the correct answer.


Ques 13 Digital Circuits

Figure I shows a 4-bit ripple carry adder realized using full adders and Figure II shows the circuit of a full-adder (FA). The propagation delay of the XOR, AND and OR gates in Figure II are 20 ns, 15 ns and 10 ns, respectively. Assume all the inputs to the 4-bit adder are initially reset to 0. At t=0 the inputs to the 4-bit adder are changed to X3X2X1X0=1100, Y3Y2Y1Y0=0100 and Z0=1. The output of the ripple carry adder will be stable at t(in ns)=

50 is the correct answer.


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