Electronics and Communication Engineering (ECE)

A second – order LTI system is described by the following state equations,

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)
  Under damped
• c)
  Critically damped
• d)
  Over damped

The power spectral density of a power signal x(t) is shown in figure below.

The average power of the signal is 

• a)
  4
• b)
  1
• c)
  6
• d)
  3

• a)
   1, 3
• b)
   1, 3, 4
• c)
  1, 2, 3
• d)
  1, 2, 3, 4

For the circuit shown in fig., let the value of β_R =0.5 and  β_F = 50. The saturation current is 10^-16 A

Q. The base-emitter voltage is

• a)
  0.53 V
• b)
  0.7 V
• c)
  0.84 V
• d)
  0.98 V

In the circuit shown, what are the values of F for EN = 0 and EN = 1, respectively?

 

• a)
  Hi-Z and D
• b)
  
• c)
  0 and 1
• d)
  0 and D

Shown below is the n-channel JFET in voltage divider bias arrangement.

V_DD = 12 V
R_S = R_D = 1.8 kΩ

R₁ = 100 kΩ

R₂ = 400 kΩ

Q.

The drain current iD is

• a)
  1.3 mA
• b)
  2.6 mA
• c)
  3.9 mA
• d)
  5.2 mA

The parameters for the transistor in circuit of fig. are V_TN = 2 V and K_n = 0.2mA / V². The power dissipated in the transistor is

• a)
  5.84 mW
• b)
  2.34 mW
• c)
  0.26 mW
• d)
  58.4 mW

An air filled rectangular waveguide with dimension where b < a < 2b is to be constructed to operate at 3GHz in dominant mode. The design frequency is at least 20% higher than the cut-off frequency of dominant mode and also at least 20% below, cut off frequency of next higher mode, determine the phase velocity.

• a)
  
• b)
  
• c)
  
• d)
  

The current gain of the transistor shown in the circuit of fig. is β = 125. The Q-point values (I_CQ , V_CEQ ) are

 

• a)
  (0.418 mA, 20.4 V)
• b)
  (0.915 mA, 14.8 V)
• c)
  (0 .915 mA, 16.23 V)
• d)
  (0.418 mA, 18.43 V)

Determine the thevenin equivalent circuit for the transistor network, external to the resistor R_L (i.e. between terminals A and B) Input Impedance of base = 2.3 kΩ, β = 100.

• a)
  
• b)
  
• c)
  
• d)
  

Consider the given circuit & waveform for the input diode (cut in voltage V_x= 0)

The waveform of output V_o is

• a)
  
• b)
  
• c)
  
• d)
  

A uniform plane wave in a lossy nonmagnetic media has

The magnitude of the wave at z = 4 m and t = T/8 is

• a)
  10.34
• b)
  5.66
• c)
  4.36
• d)
  12.60

For the circuit shown in fig. , let β = 75. The Q-point (I_CQ , V_CEQ ) is

• a)
  (4.68 mA, 16.46 V)
• b)
  (3.12 mA, 1.86 V)
• c)
  (3.12 mA, 8.46 V)
• d)
  (4.68 mA , 5.22 V)

• a)
  5.29 Ω-cm    
• b)
  11.34 Ω-cm
• c)
  9.61 Ω-cm    
• d)
  7.11 Ω-cm

• a)
  136°
• b)
  120°
• c)
  173°
• d)
  137°

• a)
  
• b)
  
• c)
  
• d)
  

The base of the number system, in which the operation is correct?

• a)
  4    
• b)
  6
• c)
  8    
• d)
  Cannot be determined

• a)
  47 mA/volt, 50 Ω, 75 kΩ
• b)
  50 mA/volt, 50 Ω, 50 kΩ
• c)
  47 mA/volt, 25 Ω, 75 kΩ
• d)
  47 mA/volt, 21 Ω, 2.642 kΩ

Consider the system shown in figure. For damping ratio of 0.5, the value of 'a’ is ____________

• a)
  0.2
• b)
  0.3
• c)
  0.25
• d)
  0.4

• a)
  
• b)
  
• c)
  
• d)
  

[Y] = ?

​ ​ ​

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  2.4, 1.2 kΩ
• b)
  1.2, 5 kΩ
• c)
  5, 1.2 kΩ
• d)
  1, 5 kΩ

• a)
  1/2 (b_xy + b_yx ) = r
• b)
  1/2 (b_xy + b_yx ) < r
• c)
  1/2 (b_xy + b_yx ) > r
• d)
  none of these

An unregulated power supply of 25 V is connected to zerer diodes and p - n diodes (cut in voltage 0.7V) as shown in figure, then the values of x and y, 7 are? 

 

• a)
  + 8.6V, + 9.3V, + 10V
• b)
  -8.6V,-9.3V, +10V
• c)
  +11.4V, + 10.7V, +10V
• d)
  -11.4V,-10.7V, +10V

• a)
  1/2    
• b)
  2.20 x10^-5
• c)
  4.39 x10^-10    
• d)
  0.005

• a)
  more accurate but less stable
• b)
  less accurate but more stable
• c)
  more accurate as well as more stable
• d)
  less accurate as well as less stable

• a)
  gain    
• b)
  3-dB noise
• c)
  noise figure    
• d)
  input impedance

• a)
  a combination of disk and cone in close approximity
• b)
  a combination of disk and cone at λ/4 spacing
• c)
  a combination of disk and cone far apart
• d)
  a combination of disk and cone at λ/2 spacing

• a)
  c(t — 2) u(t — 2)                          
• b)
  c(t — 2) u(t)
• c)
  c(t) u(t — 2)                                   
• d)
  None

• a)
  E_m = 0.3V   , f_m = 8KHz
• b)
  E_m = 1.5V , f_m = 4kHz
• c)
  E_m = 1.5 V  , f_m = 2kHz
• d)
  E_m = 3.0V    , f_m = 1kHZ

A circuit using an op - AMP is shown in the given figure it has

• a)
      Voltage series feed back
• b)
      Voltage shunt feed back
• c)
      Current shunt feed back
• d)
      Current series feed back

In the circuit shown in fig, the transformers are center tapped and the diodes are connected as shown in a bridge. Between the terminals 1 and 2 an a.c. voltage source of frequency 400 Hz is connected. Another a.c. voltage of 1.0 MHz is connected between 3 and 4. The output between 5 and 6 contains components at

• a)
  400 Hz, 1.0 MHz, 1000.4 kHz, 999.6 kHz
• b)
  400 Hz, 1000.4 kHz, 999.6 kHz
• c)
  1 MHz, 1000.4 kHz, 999.6 kHz
• d)
  1000.4 kHz, 999.6 kHz

• a)
  a = 1
  
• b)
  a = -1
• c)
  
• d)
  

• a)
  330 μs
• b)
  33 μs
• c)
  3.3 μs
• d)
  0.33 μs

The CMRR of the differential Amplifier shown Here is

• a)
  0
• b)
  2
• c)
  4
• d)
  ∞

If probability of error of PSK signal is 'x', then what will be probability of error of FSK and ASK signal. (Assume x =

• a)
  respectively   
• b)
  respectively
• c)
  respectively   
• d)
  None of these

• a)
  
• b)
  
• c)
  
• d)
  

The Q-point (V_c and I_B) for the differential amplifier shown in figure below is given by:

• a)
  V_c = 6.6 V and I_B = 1.25 μA
• b)
  V_c = 7.9 V and I_B = 1.09 μA
• c)
  V_c = 6.6 V and I_B = 1.09 μA
• d)
  V_c = 7.9 V and I_B = 1.25 μA

• a)
  
• b)
  
• c)
  
• d)
  

If wave form is given only for I period then

 

Q. Waveform x (t) is

 

• a)
  an even function with half wave symmetry.
• b)
  An odd function with half wave symmetry.
• c)
  an even function with no half wave symmetry.
• d)
  An odd function with no half wave symmetry.

Find the transfer function of the system whose asymptotic approximation is given in figure below, is

• a)
  
• b)
  
• c)
  
• d)
  

Select a suitable figure from the Answer Figures that would replace the question mark (?).

• a)
  1 
• b)
  2    
• c)
  3    
• d)
  4

Which one of the following is the general solution of the first order differential equation   = (x + y - 1)², where x, y are real?

• a)
  y = 1 + x tan^-1 (x + c) , where c is a constant
• b)
  y = 1 + x + tan (x + c) , where c is a constant
• c)
  y = 1 - x tan^-1 (x + c) , where c is a constant
• d)
  y = 1 - x + tan (x + c) , where c is a constant

• a)
  154.6 + j89.3 VA
• b)
  154.6 - j89.3 VA
• c)
  61 + j167.7 VA
• d)
  61 - j167.7 VA

All eigen values of the matrix 

• a)
  real    
• b)
  complex    
• c)
  purely imaginary    
• d)
  all negative

Q.

The mid band voltage gain Av is

• a)
  5.45    
• b)
  -5.45    
• c)
  2    
• d)
  -2

• a)
  5046%
• b)
  20.57%
• c)
  2.18%
• d)
  6.43%

• a)
  Zero initial condition
• b)
  Non-zero initial condition
• c)
  Zero final condition
• d)
  Non-zero final condition

• a)
  1
• b)
  7
• c)
  -5
• d)
  -7

The signal flow graph shown below has M number of forward path and N number of individual loops.

Q. ​What are the values of M and N ?

• a)
  M= 3 and N= 4
• b)
  M = 4 and N = 6
• c)
  M = 4 and N = 4
• d)
  M = 2 and N = 6

• a)
  0.8    
• b)
  0.7    
• c)
  0.5    
• d)
  0.6

In an air-filled waveguide, a TE mode operating at 6 GHz has

Que: The cutoff frequency is

• a)
  4.189 GHz
• b)
  5.973 GHz
• c)
  8.438 GHz
• d)
  7.946 GHz

• a)
  to maintain colour sequence
• b)
  to ensure I and Q phase correctly
• c)
  to synchronise colours
• d)
  for interlacing of horizontal lines

• a)
  1.34 dB
• b)
  3.96 dB
• c)
  6.81 dB
• d)
  None of the above.

• a)
  2f_m, f_m
• b)
  
• c)
  
• d)
  

An antenna with average noise temperature 60 K connects to a receiver through various microwave elements that can be modeled as an impedance matched attenuator with an overall loss of 2.4 dB and a physical temperatures of 275 K. The overall system noise temperature of the receiver 

Que: The average effective input noise temperature of the receiver is

• a)
  420.5 K
• b)
  320.5 K
• c)
  220.5 K
• d)
  10.5 K

• a)
  the effective base width increases and common – emitter current gain increases
• b)
  the effective base width increases and common – emitter current gain decreases
• c)
  the effective base width decreases and common – emitter current gain increases
• d)
  the effective base width decreases and common – emitter current gain decreases

• a)
  0 < k < 6.66
• b)
  0 < k < 3.33
• c)
  0 < k < I
• d)
  k > 0

• a)
  y(t) = x(t - 2) + x(t - 4)
• b)
  y(t) = (t - 4) x(t + 1)
• c)
  y(t) = (t + 4) x(t - 1)
• d)
  y(t) = (t + 5) x(t + 5)

The state-space representation for a system is

The transfer function Y(s) /U(s) is ​ ​ ​

• a)
  
• b)
  
• c)
  
• d)
  

Consider the rectangular pulse shown in figure, its fourier transform is

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  100 m    
• b)
  1000 m    
• c)
  150 m    
• d)
  1500 m

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  sin200πt
• b)
  1/2 sin200πt
• c)
  2sin 200πt
• d)
  0

Given Laplace transforms,  is

• a)
  
• b)
  
• c)
  
• d)
  Not possible to determine

• a)
  2, 3 and 4
• b)
  1,3 and 4
• c)
  1,2 and 4
• d)
  1,2 and 3

Consider the network shown in fig.

Q. The state variable may be

• a)
  i₂ , i₄
• b)
  i₂ , i_{4 ,} v_o
• c)
  i₁ , i₃
• d)
  i₁ , i₃ , i₅

• A:

  3.0

• B:

  1.0

• C:

  11

• D:

  3.02

The answer is a.

A certain random variable has the CDF (cumulative distribution function) given by:

Which of the following options is/are not correct?

• a)
  P(x ≤ 5) = 0.25
• b)
  K = 0.01
• c)
  P(5 < x ≤ 7) = 0.30
• d)
  both (a) and (b)

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  d.c. ground point
• b)
  must be floating
• c)
  The most negative voltage available in the circuit
• d)
  The most positive voltage available in the circuit

• a)
  PG/d
• b)
  PG/4

  p

  d²
• c)
  P/G(4

  p

  d²)
• d)
  

• a)
  4.36
• b)
  9.8
• c)
  19
• d)
  3.13

 Fourier analysis of waveform shown in figure

Q. The waveform is

• a)
  odd                        
• b)
  even
• c)
  either (a) or (b)
• d)
  none of these

• a)
  
• b)
  
• c)
  
• d)
  

• a)
  1.288 Hz                    
• b)
  443.5 Hz
• c)
  443.5 kHz                      
• d)
  1.288 kHz ​

• a)
  0.55
• b)
  0.45
• c)
  0.5
• d)
  0.57

Consider the points s₁ = - 3 + j4, and s₂ = - 3 - j2, in the S - plane, then for a system with the open loop transfer function   

• a)
  S₁ is on the root locus Out not S₂
• b)
  S₂ is on the root locus but not S₁
• c)
  both S₁ and S₂ are on root locus
• d)
  neither S₁ nor S₂ is or root locus