2025 103404

B.Tech 4th Semester Examination, 2024

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Choose the correct option / answer the following (Any seven questions only):

Q1.a

If X(f)X(f) is the Fourier transform of x(t)x(t), then what is the Fourier transform of x(2t)x(2t)?

a)

X(f/2)X(f/2)

b)

0.5X(f/2)0.5X(f/2)

c)

2X(2f)2X(2f)

d)

X(f)X(f)

Q1.b

Which of the following statements is true?

a)

Discrete-time signals are always periodic

b)

Continuous-time signals cannot be periodic

c)

Discrete-time signals can be periodic or aperiodic

d)

Continuous-time signals are always aperiodic

Q1.c

Find the fundamental period of x(t)=sin(5πt)+cos(7πt)x(t) = \sin(5\pi t) + \cos(7\pi t).

a)

0.2 sec

b)

0.4 sec

c)

0.8 sec

d)

1.0 sec

Q1.d

If a system's impulse response h(t)=δ(t)δ(t1)h(t) = \delta(t) - \delta(t-1), the system is:

a)

Causal

b)

Anti-causal

c)

Non-causal

d)

Time-invariant

Q1.e

Which system property ensures that the output depends only on past and present inputs?

a)

Linearity

b)

Causality

c)

Stability

d)

Time-invariance

Q1.f

Which of the following is an example of a deterministic signal?

a)

White noise

b)

Sinusoidal signal

c)

Random signal

d)

Gaussian noise

Q1.g

The impulse response of an LTI system is given by h(t)=e2tu(t)h(t) = e^{-2t}u(t). Find the system response to an input x(t)=etu(t)x(t) = e^{-t}u(t).

a)

ete2te^{-t} - e^{-2t}

b)

ete2t2\frac{e^{-t} - e^{-2t}}{2}

c)

ete2te^{-t} - e^{-2t}

d)

e3te^{-3t}

Q1.h

The step response of an LTI system is obtained by:

a)

Taking the derivative of the impulse response

b)

Integrating the impulse response

c)

Taking the Fourier transform of the impulse response

d)

Adding two impulse responses

Q1.i

The Laplace transform of eatu(t)e^{-at}u(t) is:

a)

1s+a\frac{1}{s+a}

b)

1sa\frac{1}{s-a}

c)

ss+a\frac{s}{s+a}

d)

ssa\frac{s}{s-a}

Q1.j

If a signal contains frequency components up to 5 kHz, what should be the minimum sampling rate?

a)

2.5 kHz

b)

5 kHz

c)

10 kHz

d)

20 kHz

Q.2 Solve both questions :

Q2.a

Find the inverse Laplace transform of: F(s)=s(s+2)(s+1)(s+3)(s+5)F(s) = \frac{s(s+2)}{(s+1)(s+3)(s+5)}

Q2.b

Given a system with a difference equation y[n]0.5y[n1]=x[n]y[n] - 0.5y[n-1] = x[n], determine its stability.

Q.3 Solve both questions :

Q3.a

Find the state space model of the system represented by the differential equation: d3ydt3+8d2ydt2+9dydt=3x(t)\frac{d^3y}{dt^3} + 8\frac{d^2y}{dt^2} + 9\frac{dy}{dt} = 3x(t).

Q3.b

A system is described by the equation: y(t)=3x(t)+2y(t) = 3x(t) + 2. Check whether the system is linear or not.

Q.4 Solve both questions :

Q4.a

Compute the poles and zeros of F(s)=s+1s3+7s2+10s+18F(s) = \frac{s+1}{s^3 + 7s^2 + 10s + 18}.

Q4.b

Consider a system defined by y(t)=tx(t)y(t) = tx(t). Determine whether it is linear and shift-invariant.

Q.5 Solve both questions :

Q5.a

Compute the output y[n]y[n] of an LTI system with impulse response h[n]={1,2,1}h[n] = \{1, 2, 1\} and input x[n]={2,1,3}x[n] = \{2, 1, 3\} using convolution.

Q5.b

Compute the energy and power of the signal x(t)=etu(t)x(t) = e^{-t}u(t).

Q.6 Solve both questions :

Q6.a

Find the Fourier transform of x(t)=e2tx(t) = e^{-2|t|}.

Q6.b

Find the Laplace Transform of x(t)=etu(t)x(t) = e^{-t}u(t) and determine its region of convergence.

Q.7 Solve both questions :

Q7.a

Given x(t)=sin(10t)+cos(15t)x(t) = \sin(10t) + \cos(15t), determine whether it is periodic and find the fundamental period.

Q7.b

Compute the z-transform of x[n]=bnu[n1]x[n] = -b^n u[-n-1].

Q.8 Solve both questions :

Q8.a

Find the step response of a system with impulse response h(t)=e3tu(t)h(t) = e^{-3t}u(t).

Q8.b

Determine the even and odd components of the signal x(t)=t2+3t+2x(t) = t^2 + 3t + 2.

Q.9 Write short notes on any two of the following:

Q9.a

Discuss the properties of a system with respect to linearity, causality, and stability.

Q9.b

Define Fourier series and explain its importance in signal representation.

Q9.c

State and explain the Sampling Theorem and its significance.

Q9.d

State and explain Parseval's Theorem with its application.


2024 103404

B.Tech 4th Semester Examination, 2024

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Choose the correct option/answer the following (Any seven questions only):

Q1.1

If $ X(f) $ is the Fourier transform of $ x(t) $, then what is the Fourier transform of $ x(2t) $?

a)

X(f/2)X(f/2)

b)

0.5X(f/2)0.5X(f/2)

c)

2X(2f)2X(2f)

d)

X(f)X(f)

Q1.2

Which of the following statements is true?

a)

Discrete-time signals are always periodic

b)

Continuous-time signals cannot be periodic

c)

Discrete-time signals can be periodic or aperiodic

d)

Continuous-time signals are always aperiodic

Q1.3

Find the fundamental period of $ x(t) = \sin(5\pi t) + \cos(7\pi t) $.

a)

0.2 sec

b)

0.4 sec

c)

0.8 sec

d)

1.0 sec

Q1.4

If a system's impulse response is $ h(t) = \delta(t) + \delta(t-1) $, the system is:

a)

Causal

b)

Anti-causal

c)

Non-causal

d)

Time-invariant

Q1.5

Which system property ensures that the output depends only on past and present inputs?

a)

Linearity

b)

Causality

c)

Stability

d)

Time-invariance

Q1.6

Which of the following is an example of a deterministic signal?

a)

White noise

b)

Sinusoidal signal

c)

Random signal

d)

Gaussian noise

Q1.7

The impulse response of an LTI system is given by $ h(t) = e^{-2t}u(t) $. Find the system response to an input $ x(t) = e^{-t}u(t) $.

a)

ete2t3\frac{e^{-t}-e^{-2t}}{3}

b)

ete2t2\frac{e^{-t}-e^{-2t}}{2}

c)

ete2te^{-t} - e^{-2t}

d)

ete2te3t\frac{e^{-t}-e^{-2t}}{e^{-3t}}

Q1.8

The step response of an LTI system is obtained by:

a)

Taking the derivative of the impulse response

b)

Integrating the impulse response

c)

Taking the Fourier transform of the impulse response

d)

Adding two impulse responses

Q1.9

The Laplace transform of $ e^{-at}u(t) $ is:

a)

1s+a\frac{1}{s+a}

b)

1sa\frac{1}{s-a}

c)

ss+a\frac{s}{s+a}

d)

ssa\frac{s}{s-a}

Q1.10

If a signal contains frequency components up to 5 kHz, what should be the minimum sampling rate?

a)

2.5 kHz

b)

5 kHz

c)

10 kHz

d)

20 kHz

Q.2 Solve both questions :

Q2.1

Find the inverse Laplace transform of: $ F(s) = \frac{s(s+2)}{(s+1)(s+3)(s+5)} $.

Q2.2

Given a system with a difference equation $ y[n] - 0.5y[n-1] = x[n] $, determine its stability.

Q.3 Solve both questions :

Q3.1

Find the state space model of the system represented by the differential equation: $ \frac{d^3y}{dt^3} + 8\frac{d^2y}{dt^2} + 9\frac{dy}{dt} = 3x(t) $.

Q3.2

A system is described by the equation: $ y(t) = 3x(t) + 2 $. Check whether the system is linear or not.

Q.4 Solve both questions :

Q4.1

Compute the poles and zeros of $ F(s) = \frac{s+1}{s^3 + 7s^2 + 10s + 18} $.

Q4.2

Consider a system defined by $ y(t) = tx(t) $. Determine whether it is linear and shift-invariant.

Q.5 Solve both questions :

Q5.1

Compute the output $ y[n] $ of an LTI system with impulse response $ h[n] = \{1, 2, 1\} $ and input $ x[n] = \{2, 1, 3\} $ using convolution.

Q5.2

Compute the energy and power of the signal $ x(t) = e^{-t}u(t) $.

Q.6 Solve both questions :

Q6.1

Find the Fourier transform of $ x(t) = e^{-2|t|} $.

Q6.2

Find the Laplace Transform of $ x(t) = e^{-t}u(t) $ and determine its region of convergence.

Q.7 Solve both questions :

Q7.1

Given $ x(t) = \sin(10t) + \cos(15t) $, determine whether it is periodic and find the fundamental period.

Q7.2

Compute the z-transform of $ x[n] = -b^n u[n-1] $.

Q.8 Solve both questions :

Q8.1

Find the step response of a system with impulse response $ h(t) = e^{-3t}u(t) $.

Q8.2

Determine the even and odd components of the signal $ x(t) = t^2 + 3t + 2 $.

Q.9 Write short notes on any two of the following:

Q9.1
a)

Discuss the properties of a system with respect to linearity, causality, and stability.

b)

Define Fourier series and explain its importance in signal representation.

c)

State and explain the Sampling Theorem and its significance.

d)

State and explain Parseval's Theorem with its application.


2024 V2 103404

B.Tech 4th Semester Examination, 2024

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Choose the correct option/answer the following (Any seven questions only):

Q1.1

If X(f)X(f) is the Fourier transform of x(t)x(t), then what is the Fourier transform of $ x(2t) $?

a)

X(f/2)X(f/2)

b)

0.5X(f/2)0.5X(f/2)

c)

2X(2f)2X(2f)

d)

X(f)X(f)

Q1.2

Which of the following statements is true?

a)

Discrete-time signals are always periodic

b)

Continuous-time signals cannot be periodic

c)

Discrete-time signals can be periodic or aperiodic

d)

Continuous-time signals are always aperiodic

Q1.3

Find the fundamental period of x(t)=sin(5πt)+cos(7πt)x(t) = \sin(5\pi t) + \cos(7\pi t).

a)

0.2 sec

b)

0.4 sec

c)

0.8 sec

d)

1.0 sec

Q1.4

If a system's impulse response is h(t)=δ(t)+δ(t1)h(t) = \delta(t) + \delta(t-1), the system is:

a)

Causal

b)

Anti-causal

c)

Non-causal

d)

Time-invariant

Q1.5

Which system property ensures that the output depends only on past and present inputs?

a)

Linearity

b)

Causality

c)

Stability

d)

Time-invariance

Q1.6

Which of the following is an example of a deterministic signal?

a)

White noise

b)

Sinusoidal signal

c)

Random signal

d)

Gaussian noise

Q1.7

The impulse response of an LTI system is given by h(t)=e2tu(t)h(t) = e^{-2t}u(t). Find the system response to an input x(t)=etu(t)x(t) = e^{-t}u(t).

a)

ete2t3\frac{e^{-t}-e^{-2t}}{3}

b)

ete2t2\frac{e^{-t}-e^{-2t}}{2}

c)

ete2te^{-t} - e^{-2t}

d)

ete2te3t\frac{e^{-t}-e^{-2t}}{e^{-3t}}

Q1.8

The step response of an LTI system is obtained by:

a)

Taking the derivative of the impulse response

b)

Integrating the impulse response

c)

Taking the Fourier transform of the impulse response

d)

Adding two impulse responses

Q1.9

The Laplace transform of eatu(t)e^{-at}u(t) is:

a)

1s+a\frac{1}{s+a}

b)

1sa\frac{1}{s-a}

c)

ss+a\frac{s}{s+a}

d)

ssa\frac{s}{s-a}

Q1.10

If a signal contains frequency components up to 5 kHz, what should be the minimum sampling rate?

a)

2.5 kHz

b)

5 kHz

c)

10 kHz

d)

20 kHz

Q.2 Solve both questions :

Q2.1

Find the inverse Laplace transform of: F(s)=s(s+2)(s+1)(s+3)(s+5)F(s) = \frac{s(s+2)}{(s+1)(s+3)(s+5)}.

Q2.2

Given a system with a difference equation y[n]0.5y[n1]=x[n]y[n] - 0.5y[n-1] = x[n], determine its stability.

Q.3 Solve both questions :

Q3.1

Find the state space model of the system represented by the differential equation: $ \frac{d^3y}{dt^3} + 8\frac{d^2y}{dt^2} + 9\frac{dy}{dt} = 3x(t) $.

Q3.2

A system is described by the equation: y(t)=3x(t)+2y(t) = 3x(t) + 2. Check whether the system is linear or not.

Q.4 Solve both questions :

Q4.1

Compute the poles and zeros of F(s)=s+1s3+7s2+10s+18F(s) = \frac{s+1}{s^3 + 7s^2 + 10s + 18}.

Q4.2

Consider a system defined by y(t)=tx(t)y(t) = tx(t). Determine whether it is linear and shift-invariant.

Q.5 Solve both questions :

Q5.1

Compute the output y[n]y[n] of an LTI system with impulse response $ h[n] = {1, 2, 1} $ and input x[n]={2,1,3}x[n] = \{2, 1, 3\} using convolution.

Q5.2

Compute the energy and power of the signal x(t)=etu(t)x(t) = e^{-t}u(t).

Q.6 Solve both questions :

Q6.1

Find the Fourier transform of x(t)=e2tx(t) = e^{-2|t|}.

Q6.2

Find the Laplace Transform of x(t)=etu(t)x(t) = e^{-t}u(t) and determine its region of convergence.

Q.7 Solve both questions :

Q7.1

Given x(t)=sin(10t)+cos(15t)x(t) = \sin(10t) + \cos(15t), determine whether it is periodic and find the fundamental period.

Q7.2

Compute the z-transform of x[n]=bnu[n1]x[n] = -b^n u[n-1].

Q.8 Solve both questions :

Q8.1

Find the step response of a system with impulse response h(t)=e3tu(t)h(t) = e^{-3t}u(t).

Q8.2

Determine the even and odd components of the signal x(t)=t2+3t+2x(t) = t^2 + 3t + 2.

Q.9 Write short notes on any two of the following:

Q9.1
  • Discuss the properties of a system with respect to linearity, causality, and stability.
  • Define Fourier series and explain its importance in signal representation.
  • State and explain the Sampling Theorem and its significance.
  • State and explain Parseval's Theorem with its application.
a)

Discuss the properties of a system with respect to linearity, causality, and stability.

b)

Define Fourier series and explain its importance in signal representation.

c)

State and explain the Sampling Theorem and its significance.

d)

State and explain Parseval's Theorem with its application.


2023 104305

B.Tech. 3rd Semester Examination, 2023

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Choose the correct answer of the following (any seven questions only):

Q1.1

The minimum sampling rate to avoid aliasing for $ x(t) = 5 \cos(400\pi t) $ is:

a)

100 Hz

b)

400 Hz

c)

800 Hz

d)

300 Hz

Q1.2

Which of the following system is memory less?

a)

h(t)=0h(t) = 0 for t0t \neq 0

b)

h(t)=x(t1)h(t) = x(t-1)

c)

h(t)=0h(t) = 0 for t=0t = 0

d)

h(t)=kx(t+2)h(t) = kx(t+2)

Q1.3

The ROC of $ x(t) = e^{-2t}u(t) + e^{-3t}u(t) $ is:

a)

\sigma > 2

b)

\sigma > 3

c)

\sigma > -3

d)

\sigma > -2

Q1.4

Time period of: $ x(t) = 3 \cos(20t+5) + \sin(8t-3) $ is:

a)

π/10\pi/10 sec

b)

π/20\pi/20 sec

c)

2π/52\pi/5 sec

d)

2π/152\pi/15 sec

Q1.5

The power of the signal: $ x(t) = \cos(t) $ is:

a)

1/2

b)

1

c)

2

d)

4

Q1.6

The Fourier transform exponential signal $ f(t) = e^{-at}u(t), a > 0 $ is:

a)

1a+jωt\frac{1}{-a+j\omega t}

b)

1ajωt\frac{1}{a-j\omega t}

c)

1a+jωt\frac{1}{a+j\omega t}

d)

1ajωt\frac{1}{-a-j\omega t}

Q1.7

$ x(5t) $ is:

a)

Compressed signal

b)

Expanded signal

c)

Time shifted signal

d)

Amplitude scaled signal by factor 1/5

Q1.8

Which one of the following is an example of a bounded signal?

a)

etcos(ωt)e^t \cos(\omega t)

b)

etcos(ωt)e^{-t} \cos(\omega t)

c)

etcos(ωt)e^t \cos(-\omega t)

d)

etsin(ωt)e^t \sin(\omega t)

Q1.9

The simplified valve of $ X(n) = \sum_{n=-5}^{5} \sin(2n)\delta(n+7) $ is:

a)

0

b)

-sin 10

c)

sin 10

d)

1

Q1.10

If $ X(S) = \frac{4S+1}{S^2+6S+3} $, then initial value of $ x(0) $ will be:

a)

1/3

b)

1/4

c)

4

d)

3

Q.2 Solve both questions :

Q2.1

Find the inverse Z-transform of $ X(Z) = \frac{1}{1+3Z^{-1}+2Z^{-2}} $, $ ROC: |Z| > 2 $.

Q2.2

For the system $ y(t) = 12x(t) + 7 $, check whether the system is (i) time variant/time-invariant (ii) causal/non-causal (iii) linear/non-linear.

Q.3 Solve both questions :

Q3.1

Find the even and odd components of the sequence $ X(n) = 5\delta(n+4) + 4\delta(n+3) + 3\delta(n+2) + \delta(n+1) $.

Q3.2

Determine the power of the signal $ x(t) = e^{j\alpha t}\cos(\omega_o t) $.

Q.4 Solve both questions :

Q4.1

Find the Fourier transform of $ x(t) = \frac{1}{a^2+t^2} $.

Q4.2

Find the time response of LTI system with impulse response $ h(t) = 2u(t) - 2u(t-3) $ & input is $ x(t) = 8u(t) - 8u(t-5) $.

Q.5 Solve both questions :

Q5.1

Sketch the signal $ x(-4t-3) $ as shown in figure.

Question Diagram
Q5.2

Find the convolution of the following sequence $ x(n) = 2\delta(n+1) - \delta(n) + \delta(n-1) + 3\delta(n-2) $ and $ h(n) = 3\delta(n-1) + 4\delta(n-2) + 2\delta(n-3) $.

Q.6 Solve both questions :

Q6.1

Compute the DFT of $ x(n) = \{0, 1, 2, 4\} $.

Q6.2

Compute the output of the following signals whose impulse response and input are given by $ h(t) = e^{-at}u(t) $; $ x(t) = e^{at}u(-t), a>0 $ respectively.

Q.7 Solve both questions :

Q7.1

Find the Laplace Transform of signal in the figure.

Question Diagram
Q7.2

Calculate the fundamental period of $ x(t) = 1 + \sin(\frac{2\pi}{3}t)\cos(\frac{4\pi}{5}t) $.

Q.8 Solve both questions :

Q8.1

Determine the Nyquist sampling rate and Nyquist sampling intervals for the signal $ x(t) = \text{sinc}(100\pi t)\text{sinc}(200\pi t) $.

Q8.2

Compute the state transition matrix $ \Phi(t) $ for the system represented by state equation: $ \begin{bmatrix} \dot{x}_1 \\ \dot{x}_2 \end{bmatrix} = \begin{bmatrix} 0 & 1 \\ -2 & 0 \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} $.

Q.9 Write short notes on any two of the following:

Q9.1
a)

Comparison between CTFT & DTFT

b)

Aliasing and its effect

c)

Zero-order hold circuit.

d)

Energy & Power signal.


2023 V4 104305

B.Tech. 3rd Semester Examination, 2023

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Choose the correct answer of the following (any seven questions only):

Q1.1

The minimum sampling rate to avoid aliasing for $ x(t) = 5 \cos(400\pi t) $ is:

a)

100 Hz

b)

400 Hz

c)

800 Hz

d)

300 Hz

Q1.2

Which of the following system is memory less?

a)

h(t)=0h(t) = 0 for t0t \neq 0

b)

h(t)=x(t1)h(t) = x(t-1)

c)

h(t)=0h(t) = 0 for t=0t = 0

d)

h(t)=kx(t+2)h(t) = kx(t+2)

Q1.3

The ROC of $ x(t) = e^{-2t}u(t) + e^{-3t}u(t) $ is:

a)

\sigma > 2

b)

\sigma > 3

c)

\sigma > -3

d)

\sigma > -2

Q1.4

Time period of: $ x(t) = 3 \cos(20t+5) + \sin(8t-3) $ is:

a)

π/10\pi/10 sec

b)

π/20\pi/20 sec

c)

2π/52\pi/5 sec

d)

2π/152\pi/15 sec

Q1.5

The power of the signal: $ x(t) = \cos(t) $ is:

a)

1/2

b)

1

c)

2

d)

4

Q1.6

The Fourier transform exponential signal $ f(t) = e^{-at}u(t), a > 0 $ is:

a)

1a+jωt\frac{1}{-a+j\omega t}

b)

1ajωt\frac{1}{a-j\omega t}

c)

1a+jωt\frac{1}{a+j\omega t}

d)

1ajωt\frac{1}{-a-j\omega t}

Q1.7

$ x(5t) $ is:

a)

Compressed signal

b)

Expanded signal

c)

Time shifted signal

d)

Amplitude scaled signal by factor 1/5

Q1.8

Which one of the following is an example of a bounded signal?

a)

etcos(ωt)e^t \cos(\omega t)

b)

etcos(ωt)e^{-t} \cos(\omega t)

c)

etcos(ωt)e^t \cos(-\omega t)

d)

etsin(ωt)e^t \sin(\omega t)

Q1.9

The simplified valve of $ X(n) = \sum_{n=-5}^{5} \sin(2n)\delta(n+7) $ is:

a)

0

b)

-sin 10

c)

sin 10

d)

1

Q1.10

If $ X(S) = \frac{4S+1}{S^2+6S+3} $, then initial value of $ x(0) $ will be:

a)

1/3

b)

1/4

c)

4

d)

3

Q.2 Solve both questions :

Q2.1

Find the inverse Z-transform of $ X(Z) = \frac{1}{1+3Z^{-1}+2Z^{-2}} $, $ ROC: |Z| > 2 $.

Q2.2

For the system $ y(t) = 12x(t) + 7 $, check whether the system is (i) time variant/time-invariant (ii) causal/non-causal (iii) linear/non-linear.

Q.3 Solve both questions :

Q3.1

Find the even and odd components of the sequence $ X(n) = 5\delta(n+4) + 4\delta(n+3) + 3\delta(n+2) + \delta(n+1) $.

Q3.2

Determine the power of the signal $ x(t) = e^{j\alpha t}\cos(\omega_o t) $.

Q.4 Solve both questions :

Q4.1

Find the Fourier transform of $ x(t) = \frac{1}{a^2+t^2} $.

Q4.2

Find the time response of LTI system with impulse response $ h(t) = 2u(t) - 2u(t-3) $ & input is $ x(t) = 8u(t) - 8u(t-5) $.

Q.5 Solve both questions :

Q5.1

Sketch the signal $ x(-4t-3) $ as shown in figure.

Question Diagram
Q5.2

Find the convolution of the following sequence $ x(n) = 2\delta(n+1) - \delta(n) + \delta(n-1) + 3\delta(n-2) $ and $ h(n) = 3\delta(n-1) + 4\delta(n-2) + 2\delta(n-3) $.

Q.6 Solve both questions :

Q6.1

Compute the DFT of $ x(n) = \\{0, 1, 2, 4\\} $.

Q6.2

Compute the output of the following signals whose impulse response and input are given by $ h(t) = e^{-at}u(t) $; $ x(t) = e^{at}u(-t), a>0 $ respectively.

Q.7 Solve both questions :

Q7.1

Find the Laplace Transform of signal in the figure.

Question Diagram
Q7.2

Calculate the fundamental period of $ x(t) = 1 + \sin(\frac{2\pi}{3}t)\cos(\frac{4\pi}{5}t) $.

Q.8 Solve both questions :

Q8.1

Determine the Nyquist sampling rate and Nyquist sampling intervals for the signal $ x(t) = \text{sinc}(100\pi t)\text{sinc}(200\pi t) $.

Q8.2

Compute the state transition matrix $ \Phi(t) $ for the system represented by state equation: $ \begin{bmatrix} \dot{x}_1 \\ \dot{x}_2 \end{bmatrix} = \begin{bmatrix} 0 & 1 \\ -2 & 0 \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} $.

Q.9 Write short notes on any two of the following:


2022 110406/103404

B.Tech 4th Semester Exam., 2022 (New Course)

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer any seven of the following as directed:

Q1.1

Determine the fundamental period of the signal $ x[n]=1+e^{j\frac{4\pi n}{7}}-e^{j\frac{2\pi n}{5}} $

Q1.2

Check whether the signal $ x(t)=2e^{j(t+\frac{\pi}{4})}u(t) $ is periodic or not. If periodic, then compute the periodicity.

Q1.3

Find the convolution of two signals $ x_{1}(t)=e^{-t^{2}} $ and $ x_{2}(t)=3t^{2} $

Q1.4

Let $ X(e^{j\omega}) $ be the DTFT of $ x[n] $ prove that $ X(e^{j0})=\sum_{n=-\infty}^{\infty}x[n] $

Q1.5

The step response of an LTI system when the impulse response $ h(n) $ is unit step $ u(n) $ is _________.

Q1.6

Use the convolution property of Laplace transform to determine $ y(t)=e^{at}u(t)*e^{bt}u(t) $ where symbols have their usual meanings.

Q1.7

Determine the Laplace transform of the signal $ x(t)=\cos^{3}(3t)u(t) $.

Q1.8

If $ X(z)\leftarrow\underline{z}\rightarrow x[n] $ with ROC: R, then prove that $ Z\{x[-n]\}=X(z^{-1}) $ with ROC: $ \frac{1}{R} $

Q1.9

List down the properties of region of convergence (ROC).

Q1.10

Determine the conditions on the sampling interval $ T_{s} $ so that $ x(t)=\cos(\pi t)+3\sin(2\pi t)+\sin(4\pi t) $ is uniquely represented by the discrete-time sequence $ x[n]=x(nT_{s}) $

Q.2 Solve all questions :

Q2.1

Consider a causal LTI system that is represented by the difference equation $ y[n]-\frac{3}{4}y[n-1]+\frac{1}{8}y[n-2]=2x[n] $. Find the frequency response $ H(e^{j\omega}) $ and the impulse response $ h[n] $ of the system.

Q2.2

Find the inverse DTFT of $ X(e^{j\omega})=\delta(\omega), -\pi < \omega < \pi $

Q2.3

Find the Fourier transform of $ x(n)=a^{|n|}, |a|< 1 $

Q.3 Solve all questions :

Q3.1

Find the Z-transform of $ x(n)=\begin{cases}(0.5)^{n}u(n),&n>0\\ (0.25)^{-n},&n < 0\end{cases} $

Q3.2

Find the inverse Z-transform of $ X(z)=\frac{1-\frac{1}{4}z^{-1}}{1-\frac{1}{9}z^{-1}} $ ROC: $ |z|>\frac{1}{3} $

Q3.3

Comment on the causality of the system whose transfer function is given by $ H(z)=\frac{3-4z^{-1}}{1-3.5z^{-1}+1.5z^{-2}}, |z|>3 $

Q.4 Solve all questions :

Q4.1

Derive the condition for BIBO stability.

Q4.2

Consider a continuous-time system with input $ x(t) $ and output $ y(t) $ is related by $ y(t)=x(\sin(t)) $. Is the system (i) causal and (ii) linear?

Q4.3

Sketch the signal $ x(t)=\delta(\cos t) $.

Q4.4

Find even and odd components of signal $ x(t)=e^{-2t}\cos(t) $.

Q.5 Solve all questions :

Q5.1

Compute the Fourier transform of the rectangular pulse train signal shown in Fig. 1.

Question Diagram
Q5.2

Compute the step response of the LTI system $ H(s)=\frac{6(s+1)}{s(s+3)}; Re\{s\}>0 $

Q5.3

State and prove Parseval's theorem.

Q.6 Solve all questions :

Q6.1

A system is defined as $ y(n)=x(n^{2}) $. Check whether the system is linear or non-linear, time-varying or time-invariant, causal or non-causal and memory less or memory type.

Q6.2

Compute the convolution $ y[n]=x[n]*h[n] $ where $ x[n]=u(n-1) $ and $ h[n]=\alpha^{n}u(n-1) $

Q6.3

Compute the Nyquist sampling rate for the signal $ g(t)=10\cos(50\pi)\cos^{2}(150\pi t) $

Q.7 Solve all questions :

Q7.1

Consider the causal difference equation $ y[n]-0.8y[n-1]=2x[n] $ where the input signal is $ x[n]=(\frac{1}{2})^{n}u(n) $ with $ y[-1]=0 $. Find the output response $ y[n] $.

Q7.2

Compute the inverse Z-transform of $ X(z)=\frac{z}{(1-0.5z^{-1})}; |z|<0.5 $ using the power series expansion method. Find the signal $ x[n] $.

Q7.3

Consider the stable LTI system defined by its transfer function $ H(z)=\frac{z^{2}+z-2}{z^{2}+z+0.5} $. Sketch the pole-zero plot for this transfer function and give its ROC. Is the system causal? Sketch the direct form realization of this system.

Q.8 Solve all questions :

Q8.1

Let $ x[n] $ be an arbitrary function with even and odd parts as $ x_{e}[n] $, $ x_{o}[n] $, respectively. Show that $ \sum_{n=-\infty}^{\infty}x^{2}[n]=\sum_{n=-\infty}^{\infty}x_{e}^{2}[n]+\sum_{n=-\infty}^{\infty}x_{o}^{2}[n] $

Q8.2

Perform the convolution operation between $ x[n]=\{0,0,0,0,(2),-3,1,0,0\} $ and $ h[n]=\{0,0,0,1,(2),2,0,0,0\} $ using graphical method.

Q8.3

The signal $ x(t) $ is shown in Fig. 2. Sketch the signals for $ \alpha=\frac{1}{2} $ and $ \alpha=2 $.

Question Diagram

Q.9 Write short notes on any four of the following:

Q9.1
a)

Power and energy signals

b)

Relationship between Laplace and Z-transform

c)

Initial and Final value theorems

d)

Properties of Fourier transform

e)

Zero-order hold circuit


2022 V4 110406/103404

B.Tech 4th Semester Exam., 2022 (New Course)

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer any seven of the following as directed:

Q1.1

Determine the fundamental period of the signal $ x[n]=1+e^{j\frac{4\pi n}{7}}-e^{j\frac{2\pi n}{5}} $

Q1.2

Check whether the signal $ x(t)=2e^{j(t+\frac{\pi}{4})}u(t) $ is periodic or not. If periodic, then compute the periodicity.

Q1.3

Find the convolution of two signals $ x_{1}(t)=e^{-t^{2}} $ and $ x_{2}(t)=3t^{2} $

Q1.4

Let $ X(e^{j\omega}) $ be the DTFT of $ x[n] $ prove that $ X(e^{j0})=\sum_{n=-\infty}^{\infty}x[n] $

Q1.5

The step response of an LTI system when the impulse response $ h(n) $ is unit step $ u(n) $ is _________.

Q1.6

Use the convolution property of Laplace transform to determine $ y(t)=e^{at}u(t)*e^{bt}u(t) $ where symbols have their usual meanings.

Q1.7

Determine the Laplace transform of the signal $ x(t)=\cos^{3}(3t)u(t) $.

Q1.8

If $ X(z)\leftarrow\underline{z}\rightarrow x[n] $ with ROC: R, then prove that $ Z\\{x[-n]\\}=X(z^{-1}) $ with ROC: $ \frac{1}{R} $

Q1.9

List down the properties of region of convergence (ROC).

Q1.10

Determine the conditions on the sampling interval $ T_{s} $ so that $ x(t)=\cos(\pi t)+3\sin(2\pi t)+\sin(4\pi t) $ is uniquely represented by the discrete-time sequence $ x[n]=x(nT_{s}) $

Q.2 Solve all questions :

Q2.1

Consider a causal LTI system that is represented by the difference equation $ y[n]-\frac{3}{4}y[n-1]+\frac{1}{8}y[n-2]=2x[n] $. Find the frequency response $ H(e^{j\omega}) $ and the impulse response $ h[n] $ of the system.

Q2.2

Find the inverse DTFT of $ X(e^{j\omega})=\delta(\omega), -\pi < \omega < \pi $

Q2.3

Find the Fourier transform of $ x(n)=a^{|n|}, |a|< 1 $

Q.3 Solve all questions :

Q3.1

Find the Z-transform of $ x(n)=\begin{cases}(0.5)^{n}u(n),&n>0\\ (0.25)^{-n},&n < 0\end{cases} $

Q3.2

Find the inverse Z-transform of $ X(z)=\frac{1-\frac{1}{4}z^{-1}}{1-\frac{1}{9}z^{-1}} $ ROC: $ |z|>\frac{1}{3} $

Q3.3

Comment on the causality of the system whose transfer function is given by $ H(z)=\frac{3-4z^{-1}}{1-3.5z^{-1}+1.5z^{-2}}, |z|>3 $

Q.4 Solve all questions :

Q4.1

Derive the condition for BIBO stability.

Q4.2

Consider a continuous-time system with input $ x(t) $ and output $ y(t) $ is related by $ y(t)=x(\sin(t)) $. Is the system (i) causal and (ii) linear?

Q4.3

Sketch the signal $ x(t)=\delta(\cos t) $.

Q4.4

Find even and odd components of signal $ x(t)=e^{-2t}\cos(t) $.

Q.5 Solve all questions :

Q5.1

Compute the Fourier transform of the rectangular pulse train signal shown in Fig. 1.

Question Diagram
Q5.2

Compute the step response of the LTI system $ H(s)=\frac{6(s+1)}{s(s+3)}; Re\\{s\\}>0 $

Q5.3

State and prove Parseval's theorem.

Q.6 Solve all questions :

Q6.1

A system is defined as $ y(n)=x(n^{2}) $. Check whether the system is linear or non-linear, time-varying or time-invariant, causal or non-causal and memory less or memory type.

Q6.2

Compute the convolution $ y[n]=x[n]*h[n] $ where $ x[n]=u(n-1) $ and $ h[n]=\alpha^{n}u(n-1) $

Q6.3

Compute the Nyquist sampling rate for the signal $ g(t)=10\cos(50\pi)\cos^{2}(150\pi t) $

Q.7 Solve all questions :

Q7.1

Consider the causal difference equation $ y[n]-0.8y[n-1]=2x[n] $ where the input signal is $ x[n]=(\frac{1}{2})^{n}u(n) $ with $ y[-1]=0 $. Find the output response $ y[n] $.

Q7.2

Compute the inverse Z-transform of $ X(z)=\frac{z}{(1-0.5z^{-1})}; |z|<0.5 $ using the power series expansion method. Find the signal $ x[n] $.

Q7.3

Consider the stable LTI system defined by its transfer function $ H(z)=\frac{z^{2}+z-2}{z^{2}+z+0.5} $. Sketch the pole-zero plot for this transfer function and give its ROC. Is the system causal? Sketch the direct form realization of this system.

Q.8 Solve all questions :

Q8.1

Let $ x[n] $ be an arbitrary function with even and odd parts as $ x_{e}[n] $, $ x_{o}[n] $, respectively. Show that $ \sum_{n=-\infty}^{\infty}x^{2}[n]=\sum_{n=-\infty}^{\infty}x_{e}^{2}[n]+\sum_{n=-\infty}^{\infty}x_{o}^{2}[n] $

Q8.2

Perform the convolution operation between $ x[n]=\\{0,0,0,0,(2),-3,1,0,0\\} $ and $ h[n]=\\{0,0,0,1,(2),2,0,0,0\\} $ using graphical method.

Q8.3

The signal $ x(t) $ is shown in Fig. 2. Sketch the signals for $ \alpha=\frac{1}{2} $ and $ \alpha=2 $.

Question Diagram

Q.9 Write short notes on any four of the following:


2022 110406

B.Tech 4th Semester Exam., 2022

Time 3 hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Section 1

Q1

Answer any seven of the following as directed :

a)

Determine the fundamental period of the signal $x[n] = 1 + e^{j \frac{4\pi n}{7}} - e^{j \frac{2\pi n}{5}}$

[2 Marks]
b)

Check whether the signal $x(t) = 2e^{j(t + \frac{\pi}{4})} u(t)$ is periodic or not. If periodic, then compute the periodicity.

[2 Marks]
c)

Find the convolution of two signals x1(t)=et2x_1(t) = e^{-t^2} and x2(t)=3t2x_2(t) = 3t^2

[2 Marks]
d)

Let X(ejω)X(e^{j\omega}) be the DTFT of x[n]x[n], prove that $X(e^{j0}) = \sum_{n=-\infty}^\infty x[n]$

[2 Marks]
e)

The step response of an LTI system when the impulse response h(n)h(n) is unit step u(n)u(n) is ______.

[2 Marks]
f)

Use the convolution property of Laplace transform to determine $y(t) = e^{at} u(t) * e^{bt} u(t)$ where symbols have their usual meanings.

[2 Marks]
g)

Determine the Laplace transform of the signal x(t)=cos3(3t)u(t)x(t) = \cos^3(3t) u(t).

[2 Marks]
h)

If X(z)x[n]X(z) \longleftrightarrow x[n] with ROC : RR, then prove that $Z{x[-n]} = X(z^{-1})$ with ROC : 1R\frac{1}{R}.

[2 Marks]
i)

List down the properties of region of convergence (ROC).

[2 Marks]
j)

Determine the conditions on the sampling interval TsT_s so that $x(t) = \cos(\pi t) + 3\sin(2\pi t) + \sin(4\pi t)$ is uniquely represented by the discrete-time sequence x[n]=x(nTs)x[n] = x(n T_s).

[2 Marks]
[14 Marks]

Section 2

Q2a

Consider a causal LTI system that is represented by the difference equation $y[n] - \frac{3}{4}y[n-1] + \frac{1}{8}y[n-2] = 2x[n]$ Find the frequency response H(ejω)H(e^{j\omega}) and the impulse response h[n]h[n] of the system.

[7 Marks]
Q2b

Find the inverse DTFT of X(ejω)=δ(ω),π<ωπX(e^{j\omega}) = \delta(\omega), -\pi < \omega \le \pi.

[3 Marks]
Q2c

Find the Fourier transform of x(n)=an,a<1x(n) = a^{|n|}, |a| < 1.

[4 Marks]
Q3a

Find the Z-transform of $x(n) = \begin{cases} (0.5)^n u(n), & n > 0 \ (0.25)^{-n}, & n < 0 \end{cases}$

[6 Marks]
Q3b

Find the inverse Z-transform of X(z)=114z1119z1X(z) = \frac{1 - \frac{1}{4}z^{-1}}{1 - \frac{1}{9}z^{-1}} ROC : z>13|z| > \frac{1}{3}

[4 Marks]
Q3c

Comment on the causality of the system whose transfer function is given by $H(z) = \frac{3 - 4z^{-1}}{1 - 3.5z^{-1} + 1.5z^{-2}}, |z| > 3$

[4 Marks]
Q4a

Derive the condition for BIBO stability.

[2 Marks]
Q4b

Consider a continuous-time system with input x(t)x(t) and output y(t)y(t) is related by y(t)=x(sin(t))y(t) = x(\sin(t)). Is the system (i) causal and (ii) linear?

[5 Marks]
Q4c

Sketch the signal x(t)=δ(cost)x(t) = \delta(\cos t).

[3 Marks]
Q4d

Find even and odd components of signal x(t)=e2tcos(t)x(t) = e^{-2t} \cos(t).

[4 Marks]
Q5a

Compute the Fourier transform of the signal (periodic rectangular pulse train) shown in Fig. 1.

[6 Marks]
Q5b

Compute the step response of the LTI system $H(s) = \frac{6(s+1)}{s(s+3)}; $\text{Re}\{s\} > 0

[5 Marks]
Q5c

State and prove Parseval's theorem.

[3 Marks]
Q6a

A system is defined as y(n)=x(n2)y(n) = x(n^2). Check whether the system is linear or non-linear, time-varying or time-invariant, causal or non-causal and memory less or memory type.

[5 Marks]
Q6b

Compute the convolution y[n]=x[n]h[n]y[n] = x[n] * h[n] where x[n]=u(n1)x[n] = u(n-1) and h[n]=αnu(n1)h[n] = \alpha^n u(n-1).

[7 Marks]
Q6c

Compute the Nyquist sampling rate for the signal g(t)=10cos(50πt)cos2(150πt)g(t) = 10\cos(50\pi t)\cos^2(150\pi t).

[2 Marks]
Q7a

Consider the causal difference equation y[n]0.8y[n1]=2x[n]y[n] - 0.8y[n-1] = 2x[n] where the input signal is x[n]=(12)nu(n)x[n] = (\frac{1}{2})^n u(n) with y[1]=0y[-1] = 0. Find the output response y[n]y[n].

[4 Marks]
Q7b

Compute the inverse Z-transform of X(z)=z(10.5z1);z<0.5X(z) = \frac{z}{(1-0.5z^{-1})}; |z| < 0.5. Find the signal x[n]x[n] using the power series expansion method.

[4 Marks]
Q7c

Consider the stable LTI system defined by its transfer function $H(z) = \frac{z^2 + z - 2}{z^2 + z + 0.5}$. Sketch the pole-zero plot for this transfer function and give its ROC. Is the system causal? Sketch the direct form realization of this system.

[6 Marks]
Q8a

Let x[n]x[n] be an arbitrary function with even and odd parts as xe[n],xo[n]x_e[n], x_o[n], respectively. Show that $\sum_{n=-\infty}^\infty x^2[n] = \sum_{n=-\infty}^\infty x_e^2[n] + \sum_{n=-\infty}^\infty x_o^2[n]$

[4 Marks]
Q8b

Perform the convolution operation between x[n]={0,0,0,0,2,3,1,0,0}x[n] = \{0, 0, 0, 0, \underset{\uparrow}{2}, -3, 1, 0, 0\} and h[n]={0,0,0,1,2,2,0,0,0}h[n] = \{0, 0, 0, \underset{\uparrow}{1}, 2, 2, 0, 0, 0\} using graphical method.

[6 Marks]
Q8c

The signal x(t)x(t) is shown in Fig. 2. Sketch the signals for α=1/2\alpha = 1/2 and α=2\alpha = 2 (assuming the task is to sketch $x(\alpha t)$).

[4 Marks]
Q9

Write short notes on any four of the following :

a)

Power and energy signals

b)

Relationship between Laplace and Z-transform

c)

Initial and Final value theorems

d)

Properties of Fourier transform

e)

Zero-order hold circuit

[14 Marks]

2020 EC-102 (104305)

B.Tech 3rd Semester Special Exam., 2020

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer the following as directed (any seven):

Q1.1

If the Z-transform of $ x(n) $ is $ X(z) $ then show that $ Z[x_{1}(n)*x_{2}(n)]=X_{1}(z)X_{2}(z) $

Q1.2

If the impulse response for a system is given by $ h(n)=a^{n}u(n) $, then what is the condition for the system to be BIBO stable?

Q1.3

A voltage having the laplace transform $ \frac{4s^{2}+3s+2}{7s^{2}+6s+5} $ is applied across a 2H inductor. What is the current in inductor at $ t \to \infty $ assuming zero initial condition?

Q1.4

Differentiate between Kronecker delta function and Direc delta function.

Q1.5

The step response of an LTI system when the impulse response $ h(n) $ is unit step $ u(n) $ is _________.

Q1.6

Find the Laplace transform $ f(t)=e^{3t}\cos(2t)u(t) $ where symbols have their usual meanings.

Q1.7

An LTI system is described as $ 0.5\frac{d^{2}y(t)}{dt^{2}}+2.5\frac{dy(t)}{dt}+2y(t)=\delta(t) $. Find the final value of the output response where $ y(t) $ is output and $ x(t) $ is input.

Q1.8

The period of a sequence $ x(n)=\cos(\frac{2\pi n}{3}) $ is _________.

Q1.9

The final value of step response of a causal LTI system with $ H(s)=\frac{s+1}{s+4} $ is

a)

0.5

b)

0.25

c)

1

d)

10

Q1.10

Consider two functions $ f(t)=h(t)h(3-t) $ and $ g(t)=h(t)-h(t-3) $. Are these two functions identical? Show that $ L[f(t)]=L[g(t)] $ where L is the Laplace operator.

Q.2 Solve all questions :

Q2.1

Let a system is described by the differential equation as $ \ddot{y}+3\dot{y}+2y=e^{-t} $; with initial condition $ y(0)=\dot{y}(0)=0 $. Compute the solution of the equation.

Q2.2

Let $ f(t) $ is a periodic function with periodicity T for $ t\ge0 $, then show that $ L[f(t)]=\frac{L[f_{T}(t)]}{1-e^{-sT}} $, $ s>0 $

Q2.3

Find the Laplace transform of Fig. 1.

Question Diagram

Q.3 Solve all questions :

Q3.1

State why ROC does not include any pole. Find the Z-transform of $ x(n)=\begin{cases}(0.5)^{n}u(n),&n>0\\ (0.25)^{-n},&n < 0\end{cases} $

Q3.2

Find the inverse Z-transform of $ X(z)=\frac{1-\frac{1}{4}z^{-1}}{1-\frac{1}{9}z^{-1}} $ where ROC: $ |z|>\frac{1}{3} $

Q3.3

Show that $ Z[nx(n)]=-z\frac{dX(z)}{dz} $ where $ X(z)\leftrightarrow x[n] $.

Q.4 Solve all questions :

Q4.1

Briefly explain the causality of a system.

Q4.2

Find whether the signal $ x[n]=\sin(\frac{3\pi}{4}n)+\sin(\frac{\pi}{3}n) $ is periodic or aperiodic. If periodic, then what is the periodicity of x[n]?

Q4.3

Write down the Dirichlet condition.

Q4.4

Find the Fourier transform of $ x(t)=e^{-|t|}u(t) $, and hence draw the magnitude and phase spectrums.

Q.5 Solve all questions :

Q5.1

Compute the Fourier transform of signal shown in Fig. 2: $ R_{x}(\tau)=\begin{cases}\frac{N}{2},&-B\le\tau\le B\\ 0,&elsewhere\end{cases} $

Question Diagram
Q5.2

Find the convolution of the following discrete sequences: $ x(n)=\frac{1}{3}u(n) $ and $ h(n)=\frac{1}{5}u(n) $

Q5.3

State why the realization of an ideal low-pass filter is not possible, with proper justification.

Q.6 Solve all questions :

Q6.1

A system is defined as $ y(n)=x(n^{2}) $. Check whether the system is linear or non-linear, time-varying or time-invariant, causal or non-causal, and memoryless or memory type.

Q6.2

State Parseval's theorem.

Q6.3

Sketch the signal $ x(t)=-2u(t-1) $.

Q6.4

Compute the Nyquist sampling rate for the signal $ g(t)=10\cos(50\pi)\cos^{2}(150\pi t) $

Q.7 Solve all questions :

Q7.1

Show that $ u(n)=\sum_{k=-\infty}^{n}\delta(n) $ where symbols have their usual meanings.

Q7.2

What is unit doublet? Prove that $ \int_{-\infty}^{\infty}x(t)\delta^{k}(t)dt=(-1)^{k}\frac{d^{k}x(t)}{dt^{k}}|_{t=0} $ where $ x^{k} $ is k-th derivative of function $ x(t) $ and $ \delta(t) $ is Dirac delta function.

Q7.3

A system is described by its input-output relationship as $ y[n]=\sum_{k=-\infty}^{n}x[n-k] $. Is the system memoryless, stable, causal, time-invariant and linear?

Q7.4

Find the fundamental period of signal $ x[n]=e^{j7.351\pi n} $

Q.8 Solve all questions :

Q8.1

Let $ x[n] $ be an arbitrary function with even and odd part as $ x_{e}[n] $ and $ x_{o}[n] $ respectively. Show that $ \sum_{n=-\infty}^{\infty}x^{2}[n]=\sum_{n=-\infty}^{\infty}x_{e}^{2}[n]+\sum_{n=-\infty}^{\infty}x_{o}^{2}[n] $

Q8.2

Perform the convolution operation between $ x[n]=\{0,0,0,0,(2),-3,1,0,0\} $ and $ h[n]=\{0,0,0,1,(2),2,0,0,0\} $ using graphical method.

Q8.3

Calculate the Fourier transform of $ x[n]=u[n] $.

Q.9 Write short notes on any four of the following:

Q9.1
a)

Nyquist sampling theorem

b)

Evolution of Fourier series coefficient

c)

Initial and final value theorems of Laplace transform

d)

BIBO stability

e)

Zero-order hold circuit


2020 SPECIAL EC-102 (104305)

B.Tech 3rd Semester Special Exam., 2020

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer the following as directed (any seven):

Q1.1

If the Z-transform of $ x(n) $ is $ X(z) $ then show that $ Z[x_{1}(n)*x_{2}(n)]=X_{1}(z)X_{2}(z) $

Q1.2

If the impulse response for a system is given by $ h(n)=a^{n}u(n) $, then what is the condition for the system to be BIBO stable?

Q1.3

A voltage having the laplace transform $ \frac{4s^{2}+3s+2}{7s^{2}+6s+5} $ is applied across a 2H inductor. What is the current in inductor at $ t \to \infty $ assuming zero initial condition?

Q1.4

Differentiate between Kronecker delta function and Direc delta function.

Q1.5

The step response of an LTI system when the impulse response $ h(n) $ is unit step $ u(n) $ is _________.

Q1.6

Find the Laplace transform $ f(t)=e^{3t}\cos(2t)u(t) $ where symbols have their usual meanings.

Q1.7

An LTI system is described as $ 0.5\frac{d^{2}y(t)}{dt^{2}}+2.5\frac{dy(t)}{dt}+2y(t)=\delta(t) $. Find the final value of the output response where $ y(t) $ is output and $ x(t) $ is input.

Q1.8

The period of a sequence $ x(n)=\cos(\frac{2\pi n}{3}) $ is _________.

Q1.9

The final value of step response of a causal LTI system with $ H(s)=\frac{s+1}{s+4} $ is

a)

0.5

b)

0.25

c)

1

d)

10

Q1.10

Consider two functions $ f(t)=h(t)h(3-t) $ and $ g(t)=h(t)-h(t-3) $. Are these two functions identical? Show that $ L[f(t)]=L[g(t)] $ where L is the Laplace operator.

Q.2 Solve all questions :

Q2.1

Let a system is described by the differential equation as $ \ddot{y}+3\dot{y}+2y=e^{-t} $; with initial condition $ y(0)=\dot{y}(0)=0 $. Compute the solution of the equation.

Q2.2

Let $ f(t) $ is a periodic function with periodicity T for $ t\ge0 $, then show that $ L[f(t)]=\frac{L[f_{T}(t)]}{1-e^{-sT}} $, $ s>0 $

Q2.3

Find the Laplace transform of Fig. 1.

Question Diagram

Q.3 Solve all questions :

Q3.1

State why ROC does not include any pole. Find the Z-transform of $ x(n)=\begin{cases}(0.5)^{n}u(n),&n>0\\ (0.25)^{-n},&n < 0\end{cases} $

Q3.2

Find the inverse Z-transform of $ X(z)=\frac{1-\frac{1}{4}z^{-1}}{1-\frac{1}{9}z^{-1}} $ where ROC: $ |z|>\frac{1}{3} $

Q3.3

Show that $ Z[nx(n)]=-z\frac{dX(z)}{dz} $ where $ X(z)\leftrightarrow x[n] $.

Q.4 Solve all questions :

Q4.1

Briefly explain the causality of a system.

Q4.2

Find whether the signal $ x[n]=\sin(\frac{3\pi}{4}n)+\sin(\frac{\pi}{3}n) $ is periodic or aperiodic. If periodic, then what is the periodicity of x[n]?

Q4.3

Write down the Dirichlet condition.

Q4.4

Find the Fourier transform of $ x(t)=e^{-|t|}u(t) $, and hence draw the magnitude and phase spectrums.

Q.5 Solve all questions :

Q5.1

Compute the Fourier transform of signal shown in Fig. 2: $ R_{x}(\tau)=\begin{cases}\frac{N}{2},&-B\le\tau\le B\\ 0,&elsewhere\end{cases} $

Question Diagram
Q5.2

Find the convolution of the following discrete sequences: $ x(n)=\frac{1}{3}u(n) $ and $ h(n)=\frac{1}{5}u(n) $

Q5.3

State why the realization of an ideal low-pass filter is not possible, with proper justification.

Q.6 Solve all questions :

Q6.1

A system is defined as $ y(n)=x(n^{2}) $. Check whether the system is linear or non-linear, time-varying or time-invariant, causal or non-causal, and memoryless or memory type.

Q6.2

State Parseval's theorem.

Q6.3

Sketch the signal $ x(t)=-2u(t-1) $.

Q6.4

Compute the Nyquist sampling rate for the signal $ g(t)=10\cos(50\pi)\cos^{2}(150\pi t) $

Q.7 Solve all questions :

Q7.1

Show that $ u(n)=\sum_{k=-\infty}^{n}\delta(n) $ where symbols have their usual meanings.

Q7.2

What is unit doublet? Prove that $ \int_{-\infty}^{\infty}x(t)\delta^{k}(t)dt=(-1)^{k}\frac{d^{k}x(t)}{dt^{k}}|_{t=0} $ where $ x^{k} $ is k-th derivative of function $ x(t) $ and $ \delta(t) $ is Dirac delta function.

Q7.3

A system is described by its input-output relationship as $ y[n]=\sum_{k=-\infty}^{n}x[n-k] $. Is the system memoryless, stable, causal, time-invariant and linear?

Q7.4

Find the fundamental period of signal $ x[n]=e^{j7.351\pi n} $

Q.8 Solve all questions :

Q8.1

Let $ x[n] $ be an arbitrary function with even and odd part as $ x_{e}[n] $ and $ x_{o}[n] $ respectively. Show that $ \sum_{n=-\infty}^{\infty}x^{2}[n]=\sum_{n=-\infty}^{\infty}x_{e}^{2}[n]+\sum_{n=-\infty}^{\infty}x_{o}^{2}[n] $

Q8.2

Perform the convolution operation between $ x[n]=\\{0,0,0,0,(2),-3,1,0,0\\} $ and $ h[n]=\\{0,0,0,1,(2),2,0,0,0\\} $ using graphical method.

Q8.3

Calculate the Fourier transform of $ x[n]=u[n] $.

Q.9 Write short notes on any four of the following:


2019 031510

B.Tech 5th Semester Exam., 2019

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer any seven of the following questions:

Q1.1

Find the fundamental period and frequency of the signal $ x(t)=\cos 18\pi t+\sin 12\pi t $

Q1.2

With an example, prove that cascade combination of an LTI system and its inverse system results an identity system.

Q1.3

Check whether the system $ y(t)=tx(t) $ is causal and stable.

Q1.4

What is the physical significance of convolution?

Q1.5

What do you mean by convergence of Fourier series?

Q1.6

Prove that $ x_{even}(t)\leftrightarrow Re\{a_{k}\} $ where $ x(t) $ is real and $ x(t)\leftrightarrow a_{k} $.

Q1.7

Determine the Laplace transform for the signal $ x(t)=e^{-5t}u(t-1) $.

Q1.8

For an LTI system to be causal and stable, what should be the condition on ROC and locations of poles?

Q1.9

Find the z-transform and ROC of $ x[n]=(\frac{1}{5})^{n}u(n-3) $

Q1.10

State and prove time reversal property of z-transform.

Q.2 Solve both questions :

Q2.1

Compute and plot the even and odd parts of the given discrete and continuous signals from the figures.

Question Diagram
Q2.2

Let $ x(t)=u(t-3)-u(t-5) $ and $ h(t)=e^{-3t}u(t) $. Compute:
(i) $ y(t)=x(t)*h(t) $
(ii) $ g(t)=(dx(t)/dt)*h(t) $

Q.3 Solve both questions :

Q3.1

For each of the following systems, check the properties of linearity, time-invariance, causality and BIBO stability:
(i) $ y(t)=x(t/2) $
(ii) $ y[n]=nx[n] $

Q3.2

Compute and plot the convolution $ y[n]=x[n]*h[n] $ where $ x[n]=(\frac{1}{2})^{n-2}u[n-2] $ and $ h[n]=u[n+2] $.

Q.4 Solve both questions :

Q4.1

Obtain the differential equations for the given systems.

Question Diagram
Q4.2

Explain the 'property of sifting' of discrete-time unit impulse.

Q.5 Solve both questions :

Q5.1

State and prove the following properties of continuous-time Fourier series:
(i) Frequency shifting
(ii) Periodic convolution in time-domain
(iii) Time scaling
(iv) Differentiation in time-domain

Q5.2

Calculate the Fourier series coefficients for the periodic signal
$ x(t)=\begin{cases}2&,&0\le t< 2\\ -2,&2\le t< 4\end{cases} $
with fundamental frequency $ \omega_{0}=\pi/2 $.

Q.6 Solve both questions :

Q6.1

State and prove the following properties of discrete-time Fourier transform:
(i) Time shifting
(ii) Time expansion
(iii) Multiplication of two signals in time-domain
(iv) Differentiation in frequency

Q6.2

Compute the Fourier transform of $ x[n]=(\frac{1}{4})^{|n-1|} $.

Q.7 Solve both questions :

Q7.1

Consider an LTI system whose response to the input $ x(t)=(e^{-t}+e^{-3t})u(t) $ is $ y(t)=(2e^{-t}-2e^{-4t})u(t) $. Using Laplace transforms, find the impulse response of the system. Also compute its frequency response.

Q7.2

Determine the inverse Laplace transform of $ X(s)=\frac{(s+1)}{(s+1)^{2}+4} $, $ Re\{s\}>-1 $.

Q.8 Solve both questions :

Q8.1

Determine the impulse response of the system described by the difference equation $ y[n]=\frac{1}{2}[x[n]+x[n-1]+y[n-1]] $. Assume that the system is initially relaxed.

Q8.2

Solve the following linear difference equation:
$ y[n]+\frac{1}{2}y[n-1]-\frac{1}{4}y[n-2]=0 $
Given that $ y[-1]=y[-2]=1 $.

Q.9 Solve both questions :

Q9.1

Determine all possible signals of $ x(n) $ associated with the following z-transforms:
(i) $ X(z)=\frac{1}{1-\frac{3}{2}z^{-1}+\frac{1}{2}z^{-2}} $
(ii) $ X(z)=\frac{5}{1-\frac{1}{2}z^{-1}+\frac{1}{4}z^{-2}} $

Q9.2

Obtain the z-transform and ROC of the following sequence:
$ x(n)=(\frac{1}{2})^{n}[u[n]-u[n-10]] $


2019 V4 031510

B.Tech 5th Semester Exam., 2019

Time 03 Hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Q.1 Answer any seven of the following questions:

Q1.1

Find the fundamental period and frequency of the signal $ x(t)=\cos 18\pi t+\sin 12\pi t $

Q1.2

With an example, prove that cascade combination of an LTI system and its inverse system results an identity system.

Q1.3

Check whether the system $ y(t)=tx(t) $ is causal and stable.

Q1.4

What is the physical significance of convolution?

Q1.5

What do you mean by convergence of Fourier series?

Q1.6

Prove that $ x_{even}(t)\leftrightarrow Re\{a_{k}\} $ where $ x(t) $ is real and $ x(t)\leftrightarrow a_{k} $.

Q1.7

Determine the Laplace transform for the signal $ x(t)=e^{-5t}u(t-1) $.

Q1.8

For an LTI system to be causal and stable, what should be the condition on ROC and locations of poles?

Q1.9

Find the z-transform and ROC of $ x[n]=(\frac{1}{5})^{n}u(n-3) $

Q1.10

State and prove time reversal property of z-transform.

Q.2 Solve both questions :

Q2.1

Compute and plot the even and odd parts of the given discrete and continuous signals from the figures.

Question Diagram
Q2.2

Let $ x(t)=u(t-3)-u(t-5) $ and $ h(t)=e^{-3t}u(t) $. Compute:
(i) $ y(t)=x(t)*h(t) $
(ii) $ g(t)=(dx(t)/dt)*h(t) $

Q.3 Solve both questions :

Q3.1

For each of the following systems, check the properties of linearity, time-invariance, causality and BIBO stability:
(i) $ y(t)=x(t/2) $
(ii) $ y[n]=nx[n] $

Q3.2

Compute and plot the convolution $ y[n]=x[n]*h[n] $ where $ x[n]=(\frac{1}{2})^{n-2}u[n-2] $ and $ h[n]=u[n+2] $.

Q.4 Solve both questions :

Q4.1

Obtain the differential equations for the given systems.

Question Diagram
Q4.2

Explain the 'property of sifting' of discrete-time unit impulse.

Q.5 Solve both questions :

Q5.1

State and prove the following properties of continuous-time Fourier series:
(i) Frequency shifting
(ii) Periodic convolution in time-domain
(iii) Time scaling
(iv) Differentiation in time-domain

Q5.2

Calculate the Fourier series coefficients for the periodic signal
$ x(t)=\begin{cases}2&,&0\le t< 2\\ -2,&2\le t< 4\end{cases} $
with fundamental frequency $ \omega_{0}=\pi/2 $.

Q.6 Solve both questions :

Q6.1

State and prove the following properties of discrete-time Fourier transform:
(i) Time shifting
(ii) Time expansion
(iii) Multiplication of two signals in time-domain
(iv) Differentiation in frequency

Q6.2

Compute the Fourier transform of $ x[n]=(\frac{1}{4})^{|n-1|} $.

Q.7 Solve both questions :

Q7.1

Consider an LTI system whose response to the input $ x(t)=(e^{-t}+e^{-3t})u(t) $ is $ y(t)=(2e^{-t}-2e^{-4t})u(t) $. Using Laplace transforms, find the impulse response of the system. Also compute its frequency response.

Q7.2

Determine the inverse Laplace transform of $ X(s)=\frac{(s+1)}{(s+1)^{2}+4} $, $ Re\{s\}>-1 $.

Q.8 Solve both questions :

Q8.1

Determine the impulse response of the system described by the difference equation $ y[n]=\frac{1}{2}[x[n]+x[n-1]+y[n-1]] $. Assume that the system is initially relaxed.

Q8.2

Solve the following linear difference equation:
$ y[n]+\frac{1}{2}y[n-1]-\frac{1}{4}y[n-2]=0 $
Given that $ y[-1]=y[-2]=1 $.

Q.9 Solve both questions :

Q9.1

Determine all possible signals of $ x(n) $ associated with the following z-transforms:
(i) $ X(z)=\frac{1}{1-\frac{3}{2}z^{-1}+\frac{1}{2}z^{-2}} $
(ii) $ X(z)=\frac{5}{1-\frac{1}{2}z^{-1}+\frac{1}{4}z^{-2}} $

Q9.2

Obtain the z-transform and ROC of the following sequence:
$ x(n)=(\frac{1}{2})^{n}[u[n]-u[n-10]] $


2018 031510

B.Tech 5th Semester Exam., 2018

Time 3 hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are EIGHT questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Section 1

Q1

Answer any seven questions of the following :

a)

Show δ(at)=1aδ(t)\delta(at) = \frac{1}{|a|} \delta(t) where δ(t)\delta(t) is an impulse function.

[2 Marks]
b)

Prove that u(n)=k=nδ(k)u(n) = \sum_{k=-\infty}^n \delta(k)

[2 Marks]
c)

Draw the time waveform of the signal x(t)=u(t3)u(t6)x(t) = u(t-3) - u(t-6)

[2 Marks]
d)

Determine the fundamental period of the signal x(t)=jej10tx(t) = j e^{j10t}.

[2 Marks]
e)

If ExE_x is the energy of the signal x(t)x(t), determine the energy of the signal x(atb)x(at-b) in terms of ExE_x.

[2 Marks]
f)

If x1(t)x_1(t) and x2(t)x_2(t) are odd and even signals respectively, determine whether the signal x1(t)x2(t)x_1(t) x_2(t) would be even or odd signal.

[2 Marks]
g)

Determine whether the system described by y(t)=x(2t)y(t) = x(2t) is causal.

[2 Marks]
h)

A system is described by the input-output relationship y(n)=Re[x(n)]y(n) = \text{Re}[x(n)]. Determine whether the corresponding system is linear, where Re[x(n)]\text{Re}[x(n)] represents the real part of x(n)x(n).

[2 Marks]
i)

Determine whether the system described by y(t)=ddtu(t)y(t) = \frac{d}{dt} u(t) is stable or not.

[2 Marks]
j)

Sketch the time waveform of the signal x(t)=ddt[u(t4)u(t7)]x(t) = \frac{d}{dt} [u(t-4) - u(t-7)]

[2 Marks]
[14 Marks]

Section 2

Q2a

Determine convolution of a rectangular signal x(t)x(t) with itself. x(t)x(t) is described as $x(t) = \begin{cases} A & -T < t < T \ 0 & \text{otherwise} \end{cases}$ Draw the sketch of the convolved signal.

[8 Marks]
Q2b

Prove that x(t)u(t)=tx(τ)dτx(t) * u(t) = \int_{-\infty}^t x(\tau) d\tau

[3 Marks]
Q2c

Prove that u(t)u(t)=r(t)u(t) * u(t) = r(t).

[3 Marks]
Q3a

Determine the overall impulse response of the system shown in the figure below : [Diagram: Cascade connection of two systems with impulse responses h1(n)h_1(n) and $h_2(n)$] where h1(n)=δ(n)aδ(n1)h_1(n) = \delta(n) - a\delta(n-1) and h2(n)=(1/2)nu(n)h_2(n) = (1/2)^n u(n).

[5 Marks]
Q3b

Evaluate the unit step response of the LTI system represented by h(n)=δ(n)δ(n2)h(n) = \delta(n) - \delta(n-2)

[5 Marks]
Q3c

The impulse response of a system is given by h(n)=(1/2)nu(n+2)h(n) = (1/2)^n u(n+2). Determine whether this system is causal.

[4 Marks]
Q4a

From the given Fourier series x(t)=k=akejkω0tx(t) = \sum_{k=-\infty}^\infty a_k e^{j k \omega_0 t} derive the relation to determine the Fourier series coefficients aka_k. Given x(t)x(t) is periodic with period TT.

[4 Marks]
Q4b

Determine the Fourier series coefficients of the following : $x(t) = 1 + \sin \omega_0 t + 2\cos \omega_0 t + \cos(2\omega_0 t + \pi/4)$

[4 Marks]
Q4c

Prove the following properties of the Fourier series :

a)

Time shifting

[2 Marks]
b)

Time reversal

[2 Marks]
c)

Multiplication

[2 Marks]
[6 Marks]
Q5a

Determine the Fourier transform of the following signals :

a)

x(t)=e2t1x(t) = e^{-2|t-1|}

[3 Marks]
b)

x(t)=(eatcosω0t)u(t)x(t) = (e^{-at} \cos \omega_0 t) u(t), a>0a > 0

[3 Marks]
[6 Marks]
Q5b

Determine the inverse Fourier transform of X(jω)=2πδ(ω)+πδ(ω4π)+πδ(ω+4π)X(j\omega) = 2\pi \delta(\omega) + \pi \delta(\omega - 4\pi) + \pi \delta(\omega + 4\pi)

[4 Marks]
Q5c

Prove that the Fourier transform of a real and even signal is real and even.

[4 Marks]
Q6a

Given that x(n)x(n) has Fourier transform X(ejω)X(e^{j\omega}). Using Fourier transform properties or otherwise, determine the Fourier transform of the following signals :

a)

x1(n)=x(1n)+x(1n)x_1(n) = x(1-n) + x(-1-n)

[3 Marks]
b)

x2(n)=x(n)+x(n)2x_2(n) = \frac{x^*(-n) + x(n)}{2}

[3 Marks]
c)

x3(n)=(n1)2x(n)x_3(n) = (n-1)^2 x(n)

[3 Marks]
[9 Marks]
Q6b

Prove the following properties of discrete-time Fourier transform :

a)

Conjugation

[1 Marks]
b)

Differentiation in frequency

[2 Marks]
c)

Convolution

[2 Marks]
[5 Marks]
Q7a

If the input to an LTI system is x(t)=e3tu(t)x(t) = e^{-3t} u(t) then the output is y(t)=[ete2t]u(t)y(t) = [e^{-t} - e^{-2t}] u(t). Determine the system function of this system. Comment on the stability of the system.

[6 Marks]
Q7b

Given X(s)=s+2s2+7s+12X(s) = \frac{s+2}{s^2 + 7s + 12} determine the signal x(t)x(t) when

a)

ROC Re(s)>4\text{Re}(s) > -4

[2 Marks]
b)

ROC Re(s)<3\text{Re}(s) < -3

[3 Marks]
c)

ROC 4<Re(s)<3-4 < \text{Re}(s) < -3

[3 Marks]
[8 Marks]
Q8a

Determine the z-transform of the following signals. Sketch their pole-zero plot and indicate the region of convergence :

a)

x1(n)=(1/2)n+1u(n+3)x_1(n) = (1/2)^{n+1} u(n+3)

[3 Marks]
b)

x2(n)=2nu(n)+(1/4)nu(n1)x_2(n) = 2^n u(-n) + (1/4)^n u(n-1)

[3 Marks]
[6 Marks]
Q8b

Consider an even sequence x(n)x(n) with rational z-transform X(z)X(z). From the definition of z-transform, show that X(z)=X(1/z)X(z) = X(1/z).

[4 Marks]
Q8c

Determine the system function for the causal LTI system with difference equation y(n)32y(n1)+12y(n2)=x(n1)y(n) - \frac{3}{2}y(n-1) + \frac{1}{2}y(n-2) = x(n-1) and also determine its impulse response.

[4 Marks]

2016 031610

B.Tech 6th Semester Exam., 2016

Time 3 hours
Full Marks 70
Instructions:
  • The marks are indicated in the right-hand margin.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Section 1

Q1

Choose the correct answer (any seven) :

a)

Let δ(t)\delta(t) denote the delta function. The value of the integral δ(t)cos(3t2)dt\int_{-\infty}^{\infty} \delta(t) \cos(\frac{3t}{2}) dt is

a)

1

b)

-1

c)

0

d)

π/2\pi/2

[2 Marks]
b)

If a signal f(t)f(t) has energy EE, the energy of signal f(2t)f(2t) is equal to

a)

EE

b)

E/2E/2

c)

2E2E

d)

4E4E

[2 Marks]
c)

The system y(t)=ex(t)y(t) = e^{x(t)} is

a)

stable and causal

b)

non-causal and stable

c)

unstable and causal

d)

unstable and non-causal

[2 Marks]
d)

The system represented by h(n)=(0.99)nu(n+2)h(n) = (0.99)^n u(n+2) is

a)

unstable because it is an FIR system

b)

stable because it is an IIR system

c)

unstable because it does not obey BIBO stability criteria

d)

stable because it obeys BIBO stability criteria

[2 Marks]
e)

The impulse response of a system is h(t)=δ(t0.5)h(t) = \delta(t-0.5). If two such systems are cascaded, the impulse response of the overall system will be

a)

0.5δ(t0.25)0.5\delta(t-0.25)

b)

δ(t0.25)\delta(t-0.25)

c)

δ(t1)\delta(t-1)

d)

0.5δ(t1)0.5\delta(t-1)

[2 Marks]
f)

If x(t)x(t) is odd, then its Fourier series coefficients must be

a)

real and odd

b)

imaginary and odd

c)

real and even

d)

imaginary and even

[2 Marks]
g)

The Laplace transform of a unit ramp function starting at t=at=a is

a)

1(s+a)2\frac{1}{(s+a)^2}

b)

eas(s+a)2\frac{e^{-as}}{(s+a)^2}

c)

eass2\frac{e^{-as}}{s^2}

d)

as2\frac{a}{s^2}

[2 Marks]
h)

If L[f(t)]=2(s+1)s2+2s+5L[f(t)] = \frac{2(s+1)}{s^2 + 2s + 5}, then f(0+)f(0^+) and f()f(\infty) are given by

a)

0, 2 respectively

b)

2, 0 respectively

c)

0, 1 respectively

d)

2/5, 0 respectively

[2 Marks]
i)

If the impulse response of a discrete time system is h(n)=5nu(n1)h(n) = -5^n u(-n-1), then the system function H(z)H(z) is equal to

a)

zz5\frac{-z}{z-5} and the system is stable

b)

zz5\frac{z}{z-5} and the system is stable

c)

zz5\frac{-z}{z-5} and the system is unstable

d)

zz5\frac{z}{z-5} and the system is unstable

[2 Marks]
j)

The output of discrete LTI system is always identical to the input signal, when the unit impulse response h(n)h(n) is

a)

unit step

b)

unit impulse

c)

all ones

d)

ramp

[2 Marks]
[14 Marks]

Section 2

Q2a

For the signal x(t)x(t) shown in the figure below, find the signals (i) x(t2)x(t-2), (ii) x(2t+3)x(2t+3), (iii) x(32t)x(\frac{3}{2}t) and (iv) x(t+1)x(-t+1):

[7 Marks]
Q2b

Find whether the following signals are periodic or not : (i) x(t)=2cos(10t+1)sin(4t+1)x(t) = 2\cos(10t+1) - \sin(4t+1) (ii) cos60πt+sin50πt\cos 60\pi t + \sin 50\pi t (iii) 2u(t)+2sin2t2u(t) + 2\sin 2t (iv) 3cos4t+2sin2πt3\cos 4t + 2\sin 2\pi t (v) u(t)12u(t) - \frac{1}{2} (vi) sin2t\sin^2 t

[7 Marks]
Q3a

Check whether the following systems are linear or not : (i) dydt+3ty(t)=t2x(t)\frac{dy}{dt} + 3ty(t) = t^2 x(t) (ii) dy(t)dt+2y(t)=x2(t)\frac{dy(t)}{dt} + 2y(t) = x^2(t) (iii) y(t)=tx(τ)dτy(t) = \int_{-\infty}^t x(\tau) d\tau (iv) dydt+2y(t)=x(t)dx(t)dt\frac{dy}{dt} + 2y(t) = x(t) \frac{dx(t)}{dt} (v) y(n)=Ax(n)+By(n) = Ax(n) + B (vi) y(n)=2x(n)+1x(n1)y(n) = 2x(n) + \frac{1}{x(n-1)} (vii) y(n)=nx(n)y(n) = nx(n)

[7 Marks]
Q3b

For each of the following systems, determine whether the system is time-invariant : (i) y(t)=tx(t)y(t) = tx(t) (ii) y(t)=x(t)cos(50πt)y(t) = x(t)\cos(50\pi t) (iii) y(t)=x(t2)y(t) = x(t^2) (iv) y(t)=x(t)y(t) = x(-t) (v) y(t)=ex(t)y(t) = e^{x(t)} (vi) y(n)=x(2n)y(n) = x(2n) (vii) y(n)=x(n)+nx(n1)y(n) = x(n) + nx(n-1) (viii) y(n)=x2(n1)y(n) = x^2(n-1)

[7 Marks]
Q4a

Prove that the output of a discrete time system can be represented as a weighted sum of shifted impulse responses.

[7 Marks]
Q4b

Obtain the convolution of the following sequence : x(n)=u(n)u(n7)x(n) = u(n) - u(n-7), h(n)=u(n1)u(n4)h(n) = u(n-1) - u(n-4)

[7 Marks]
Q5

Obtain the differential equations governing the following systems :

a)

A mechanical translational system consisting of a mass MM, a spring with constant kk, and a damper with constant BB, with a force f(t)f(t) applied and displacement x(t)x(t) indicated.

b)

A series RLC circuit with resistor RR, inductor LL, and capacitor CC driven by a voltage source v(t)v(t).

c)

An electrical network with a 2Ω2\Omega resistor, a 1 H1\text{ H} inductor, and a 2 F2\text{ F} capacitor, with input voltage v(t)v(t) and output y(t)y(t).

[14 Marks]
Q6

Find cosine Fourier series of half-wave rectified sine function.

[14 Marks]
Q7a

For the waveform shown in the figure below (a periodic rectangular pulse train), find the Laplace transform.

[7 Marks]
Q7b

For the waveform shown in the figure below (a single triangular pulse), find the Laplace transform.

[7 Marks]
Q8

Using Laplace transform, solve the following differential equation : $\frac{d^3y(t)}{dt^3} + 7\frac{d^2y(t)}{dt^2} + 16\frac{dy(t)}{dt} + 12y(t) = x(t)$ if \frac{dy(0^-)}{dt} = 0$; $\frac{d^2y(0^-)}{dt^2} = 0, y(0)=0y(0^-) = 0 and x(t)=δ(t)x(t) = \delta(t)

[14 Marks]
Q9

Find the impulse response and step response for the following system : $y(n) - \frac{3}{4}y(n-1) + \frac{1}{8}y(n-2) = x(n)$

[14 Marks]

2015 031610

B.Tech 6th Semester Exam., 2015

Time 3 hours
Full Marks 70
Instructions:
  • All questions carry equal marks.
  • There are NINE questions in this paper.
  • Attempt FIVE questions in all.
  • Question No. 1 is compulsory.

Section 1

Q1

Answer any seven of the following questions :

a)

Define causal system.

[2 Marks]
b)

What is continuous time signal?

[2 Marks]
c)

Write the condition of existence for Laplace transform.

[2 Marks]
d)

Define Fourier transform of a sequence.

[2 Marks]
e)

What is DTFT pair?

[2 Marks]
f)

What is Fourier integral?

[2 Marks]
g)

What are analogous systems?

[2 Marks]
h)

Find the z-transform of discrete-time unit impulse δ(n)\delta(n).

[2 Marks]
i)

What is z-transform of Aδ(nm)A\delta(n-m)?

[2 Marks]
j)

Define region of convergence (ROC).

[2 Marks]
[14 Marks]

Section 2

Q2a

Sketch the following signal : x(t)=A[U(t+a)U(ta)]x(t) = A[U(t + a) - U(t - a)] for a>0a > 0 Also determine whether the given signal is a power signal or an energy signal or neither.

[7 Marks]
Q2b

Show that a system with excitation x(t)x(t) and response y(t)y(t) described by y(t)=x(t/2)y(t) = x(t/2) is linear, time-variant, non-causal.

[7 Marks]
Q3a

Compare energy and power signals.

[7 Marks]
Q3b

What are the elementary signals? Explain with suitable diagrams.

[7 Marks]
Q4a

Compare force-voltage analogy with force-current analogy.

[7 Marks]
Q4b

Obtain the solution of the differential equation given below using Laplace transform : $2 \frac{dx}{dt} + 8x = 10$ Given x(0+)=2x(0^+) = 2.

[7 Marks]
Q5a

The Laplace transform of f(t)f(t) is given by $F(s) = \frac{4}{s(s+2)}$ Find the final value using the final-value theorem and verify the result by determining f(t)f(t) using inverse Laplace transform.

[7 Marks]
Q5b

Find the inverse Fourier transform of δ(ωω0)\delta(\omega - \omega_0).

[7 Marks]
Q6a

Write the Dirichlet's conditions for Fourier series.

[7 Marks]
Q6b

Obtain Fourier series representation of the periodic rectangular waveform which is defined as $x(t) = \begin{cases} 0 & \text{for } t \in (-T/2, -T/4) \ A & \text{for } t \in (-T/4, T/4) \ 0 & \text{for } t \in (T/4, T/2) \end{cases}$

[7 Marks]
Q7a

Explain the concept of negative frequency. Find the Fourier transform of the everlasting sinusoid cosω0t\cos \omega_0 t.

[7 Marks]
Q7b

Explain the linearity and time-scaling properties of Fourier transform.

[7 Marks]
Q8a

Discuss the classification of turbines based on head.

[7 Marks]
Q8b

Define specific speed. What are different types of turbine based on specific speed?

[7 Marks]
Q9

A hydroelectric station is to be supplied with 10 m3/s10 \text{ m}^3/\text{s} of water through a penstock which has a friction factor of 0.016. The maximum normal head on the penstock is 50 kg/cm250 \text{ kg/cm}^2 and a water hammer over pressure of 20% is anticipated over normal pressure. The safe stress in the steel used is presumed to be 3000 kg/cm23000 \text{ kg/cm}^2. The ready penstocks at site are likely to cost ₹ 65000 per tonne including erection charges. The life of the project is 50 years and the rate of interest is 7%. It is proposed to sell the energy at the rate of ₹ 3.03 per kWh. What should be the optimum diameter of the penstock, given that the OMR costs 5%? Assume the turbine efficiency to be 90% and the annual load factor as 0.4.

[14 Marks]

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