## Transmission lines and waveguide 5th ND11 EC2305

ANNA UNIVERSITY OF TECHNOLOGY, COIMBATORE
B.E/B.TECH. DEGREE EXAMINATIONS: NOV/DEC 2011
REGULATIONS:2008 FIFTH SEMESTER : ECE

EC2305/080290031-TRANSMISSION LINES AND WAVEGUIDES

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PART-A ( 10 X 2 = 20 MARKS) ANSWER ALL QUESTIONS

1. Define characteristic impedance and propagation constant of a transmission line.
2. What is the physical significance of an infinite line?
3. Write some applications of smith chart.
4. Distinguish between single stub and double stub matching.
5. What are guided waves?
6. Plot the frequency Vs attenuations characteristic curve of TM and TE waves guided between parallel conducting plates.
7. Write the expression of TE waves in rectangular guide.
8. What is the dominant mode for the TE and TM waves in the rectangular waveguide?
9. What is the resonant frequency of a microwave resonator?
10. Distinguish between wave guide and cavity resonator.

PART-B  (5 x 16 = 80 MARKS) ANSWER ALL QUESTIONS

11. a) Obtain the general solution for voltages and currents at any point on the transmission line
(OR)
b) i) Derive the condition for distortion less line (6)
ii) A cable has the following parameters (10)
R= 48.75 ?/Km
L= 1.09 mH/Km
G= 38.75 µmhos/Km
C= 0.059 µf/Km
Determine the characteristics impedance, propagation constant and wavelength for a source of  F= 1600 Hz and Es= 1 volt

12. a) A load of (50 – j 100) ? is connected across a 50 ? line. Design a short circuited stub to provide matching between the two at a signal frequency of 30 MHz using smith chart.
(OR)
b) i) A 70 ? line is used at a frequency where wavelength equals 80cm terminated by a load of 140+j91 ?. Find the reflection co-efficient and VSWR using smith chart. (8)
ii) What is SWR? Derive SWR in terms of reflection co-effiecient. (8)

13. a) Derive the attenuation constant of TE waves in parallel plane waveguide.
(OR)
b) i) Derive the field components of TM waves between parallel plates propagating in z  direction. (8)
ii) For a frequency of 6GHz and plane separation of 7cm, find cut-off frequency and phase velocity for TE10 mode. (8) .

14. a) A X band rectangular waveguide has inner dimensions of a = 2.3cm, b =1 cm. calculate the  cut-off frequency for the following modes. TE10, TE20, TM11, TM12. Also check which of the  following modes propagate along the waveguide when the signal frequency is 10GHz
(OR)
b)i) TEM waves cannot exist in a single conductor – justify using Maxwell’s equation (6)
ii) Derive the attenuation constant of TE waves in rectangular waveguide (10)

15. a) i) Determine the solution of electric and magnetic fields of TM waves guided along  circular waveguide (8)
ii) Calculate the resonant frequency of rectangular resonator with dimensions a=3cm,  b=2cm, and d=4cm if the operating mode is TE101 . (8)
(OR)
b) Derive the Q factor of rectangular cavity resonator for TE101 mode.

## Electronic Circuits II 4th AM11 EC2251

Question Paper Code: 11283
B.E./B.Tech.Degree Examinations, April/May 2011
Regulations 2008
Fourth Semester
Electronics and Communication Engineering
EC 2251 Electronics Circuits II
( Common to PTEC 2251 Electronics Circuits II for B.E.(Part -Time) Third
Semester ECE - Regulations 2009)

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Part A - (10 x 2 = 20 marks)

1. What i s `return ratio' of a feedback amplifier?
2. State the e®ect on output resistance and on input resistance of amplifier when current shunt feedback i s employed.
3. A Weinbridge oscillator is used for operations at 9 kHz. If the value of the resistance R is 100 kohm, what i s the value of C required?
4. A tuned collector oscillator in a radio receiver has a fixed inductance of 60 ¹H and has to be tunable over the frequency band of 400 KHz to 1200 KHz. Find the range of variable capacitor to be used.
5. What i s the e®ect of cascading n stages of identical single tuned amplifiers (synchronously tuned) on the overall 3 dB bandwidth?
6. What is narrow band neutralization?
7. What is meant by clipper circuit?
8. What are the applications of bistable multivibrator?
9. What are the applications of Blocking oscillator?
10. Sketch and define the `slope error' of a voltage sweep waveform.

Part B - (5 x 16 = 80 marks)

11. (a) (i) Sketch the block diagram of a feedback amplifier and derive the expressions for gain
(1) with positive feedback and (2) with negative feedback. State the advantages of negative feedback. (6)
(ii) An amplifier, without feedback, has a voltage gain of 400, lower cut-off frequency f1 = 50 Hz, upper cut-ff frequency f2 = 200 KHz and a distortion of 10%.
Determine the amplifier voltage gain, lower cut-ff frequency and upper cut-off frequency and distortion, when a negative feedback i s applied with feedback ratio of 0.01. (5)
(iii) An amplifier, with feedback, has voltage gain of 100. When the gain without feedback changes by 20% and the gain with feedback should not vary more than 2%. If so, determine the values of open loop Gain A and feedback ratio fi. (5)
OR
11. (b) (i) Draw the circuits of voltage shunt and current series feedback amplifiers and derive the expressions for input impedance Rif . (10)
(ii) Discuss Nyquist criterion for stability of feedback amplifiers, with the help of Nyquist plot and Bode plot. (6)

12. (a) (i) Sketch the basic block diagram of an oscillator and explain how it works. If the gain of the amplifier is A and the feedback factor i s fi, sketch the output waveforms for the three cases (1) jAfij > 1, (2) jAfij = 1 and (3) jAfij < 1.
Derive the conditions of sustained oscillations. (10)
(ii) Make a table of comparison of RC phase shift oscillator and Wien-bridge oscillator bringing out the similarities and di®erences. (6)
OR
12. (b) (i) Explain the working of a Colpitts oscillator with a neat circuit diagram and derive the frequency of oscillation. (8)
(ii) In a Colpitt's oscillator, the value of the inductor and capacitors in the tank circuit are L = 40 mH, C1 = 100 pF and C2 = 500 pF. (8)
(1) Find the frequency of oscillation.
(2) If the output voltage is 10 V, find the feedback voltage at the input side of the amplifier.
(3) Find the minimum gain, if the frequency is changed by charging `L' alone.
(4) Find the value of C1 for a gain of 10 if C2 i s kept constant as 500 pF. Also find the resulting new frequency.

13. (a) (i) Draw the circuit diagram and the equivalent circuit of a capacitor-coupled single tuned amplifier and explain its operation. Derive the equations for voltage gain and for 3-dB bandwidth. Sketch also the frequency response of the amplifier.
(12)
(ii) A single tuned transistor amplifier is used to amplify modulated RF carrier of 600 kHz and bandwidth of 15 kHz. The circuit has total output resistance Rt = 20 k and output-capacitance C0 = 50 pF. Calculate the values of inductance and capacitance of tuned circuit. (4)
OR
13. (b) (i) Explain, with suitable circuit diagrams, Hazeltine neutralization and coil neutralization techniques. (8)
(ii) A Class C tuned amplifier has RL = 6 k­ and the tank circuit is required to have QL = 80. Calculate the values of L and C of the tank circuit. Assume Vcc = 20V, resonant frequency = 5 MHz and worst case power dissipation = 20 mW. (8)

14. (a) (i) With necessary circuit diagrams and waveforms, explain the operation of the following: (1) Positive clipper, (2) Negative clipper, (3) Biased clipper and (4) Combinational (Two-way) clipper. (12)
(ii) Mention the applications of clamping circuits. (4)
OR
14. (b) (i) With neat circuit diagram and suitable wave forms, explain the operation of a collector coupled transistor monostable multivibrator. (8)
(ii) Design a Schmitt trigger circuit to have VCC = 12 V, UTP = 5 V, LTP = 3V and IC = 2 mA using two silicon NPN transistors with hfe(min) = 100 and I2 = 0:1IC2. (8)

15. (a) (i) Draw and explain the triggering circuit used in monostable blocking oscillator.(8)
(ii) Explain, with the help of circuits and wave-forms, the operation of RC-controlled push-pull astable blocking oscillator with emitter timing. (8)
OR
15. (b) (i) Design a UJT relaxation oscillator to generate a saw tooth wave form at a frequency of 500 Hz.
Assume the supply voltage VBB = 20 V, VP = 2:9 V, VV = 1:118 V, IP = 1:6 mA and IV = 3:5 mA. State further assumptions made,if any. Sketch the circuit designed. (8)
(ii) Sketch a current time base circuit and explain its working with the help of relevant waveforms. (8)

## Control System 4th AM11 EC2255

B.E./B.Tech.Degree Examinations, April/May 2011
Regulations 2008
Fourth Semester
Electronics and Communication Engineering
EC 2255 Control Systems

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Part A - (10 x 2 = 20 marks)

1. Define open-loop and closed-loop control systems.
2. Write down the transfer function of the system whose block diagram is shown below.

3. How a control system i s classified depending on the value of damping?
4. Why derivative controller is not used in control system?
5. What i s meant by `Corner frequency' in frequency response analysis?
6. Draw the circuit of lead compensator and draw its pole zero diagram.
7. State the rule for obtaining the breakaway point in root locus.
8. Define stability of a system.
9. Name the methods of state space representation for phase variables.
10. What i s meant by quantization?

Part B - (5 x 16 = 80 marks)

11. (a) (i) Consider the mechanical system shown below. Identify the variables and write
the di®erential equation. (6)
(ii) Draw the torque-voltage electrical analogous circuit for the following mechanical
system shown . (4)
(iii) Obtain the transfer function of the following electrical network. (6)

## Data Structure and OOP in C++ 3rd AM10 EC2202

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010
Third Semester
Electronics and Communication Engineering
EC2202 — DATA STRUCTURES AND OBJECT ORIENTED
PROGRAMMING IN C ++
(Regulation 2008)

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PART A — (10 ??2 = 20 Marks)

1. How is a class declared in C++?
2. What is a scope resolution operator and how can it be used for global variable?
3. What is meant by binding?
4. How the pointer is implemented in C++?
5. Write any two data structures used in Operating System?
6. What are the representations of Big and small ‘O’ notations?
7. How many trees are possible with 3 nodes?
8. What is a spanning tree?
9. What is the feature of bucket sort algorithm?
10. Define dynamic programming.

PART B — (5 ??16 = 80 Marks)

11. (a) (i) Give the syntax and usage of the reserved word inline with two examples. (8)
(ii) Explain the importance of constructors and destructors with example. (8)
Or
(b) What is operator overloading? Overload the numerical operators ‘+’and ‘/’ for complex numbers “addition” and “division” respectively. (16)

12. (a) (i) Define friend class and specify its importance. Explain with suitable example. (8)
(ii) Discuss Virtual function and polymorphism with example. (8)
Or
(b) (i) Explain the concept of inheritance by considering an example of “vehicle”. (8)
(ii) Explain the operators used for dynamic memory allocation with examples. (8)

13. (a) (i) Explain Priority Queues and how are binary heaps used in that. (8)
(ii) Explain the properties of heap. (8)
Or
(b) (i) Write a C ++ program to implement Stack and its operations PUSH and POP. (10)
(ii) What is hashing? Classify hashing functions based on the various methods. (6)

14. (a) (i) Traverse the tree given below using Inorder, Preorder and Postorder traversals. (10)
(ii) Convert the expression ((A + B) * C - (D - E) ^ (F + G)) to equivalent Prefix and postfix notations. (6)
Or
(b) (i) Convert the given graph with weighted edges to minimal spanning tree. (10)
(ii) Write a short note on AVL trees. (6)

15. (a) Explain the algorithm of Quicksort by sorting the following set of numbers as an example:
42 47 52 57 62 37 32 27 22
Or
(b) Describe divide and conquer technique with the help of mergesort. (16)

## Communication Theory 4th AM10 EC2252

B.E./B.Tech.Degree Examinations,Apr/May 2010
Regulations 2008
Fourth Semester
Electronics and Communication Engineering
EC2252 Communication Theory

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Part A - (10 x 2 = 20 Marks)

1. How many AM broadcast stations can be accommodated in a 100 kHz bandwidth if the highest frequency modulating a carrier i s 5 kHz?
2. What are the causes of linear distortion?
3. Draw the block diagram of a method for generating a narrowband FM signal.
4. A carrier wave of frequency 100 MHz i s frequency modulated by a signal 20 sin(200¼ £ 103t):
What i s bandwidth of FM signal if the frequency sensitivity of the modulation is 25kHz=V .
5. When i s a random process called deterministic?
6. A receiver connected to an antenna of resistance of 50­ has an equivalent noise resistance of 30­. Find the receiver noise figure.
7. What are the characteristics of superheterodyne receivers?
8. What are the methods to improve FM threshold reduction?
9. Define entropy function.
10. Define Rate Bandwidth and Bandwidth eficiency.

Part B - (5 x 16 = 80 Marks)

11. (a) (i) Draw an envelope detector circuit used for demodulation of AM and ex-plain its operation. (10)
(ii) How SSB can be generated using Weaver's method? Illustrate with a neat block diagram. (6)
OR
11. (b) (i) Discuss in detail about frequency translation and frequency division mul-tiplexing technique with diagrams. (10)
(ii) Compare Amplitude Modulation and Frequency Modulation.(6)

12. (a) (i) Using suitable Mathematical analysis show that FM modulation produces in¯nite sideband. Also deduce an expression for the frequency modulated output and its frequency spectrum. (10)
(ii) How can you generate an FM from PM and PM from FM? (6)
OR
12. (b) (i) A 20 MHz is frequency modulated by a sinusoidal signal such that the maximum frequency deviation i s 100 kHz. Determine the modulation index and approximate bandwidth of the FM signal for the following modulating signal frequencies,
(1) 1 kHz (2) 100 kHz and (3) 500 kHz. (8)
(ii) Derive the time domain expressions of FM and PM signals.(8)

13. (a) (i) Give a random process, X(t) = Acos(!t+µ), where A and ! are constants and µ is a uniform random variable. Show that X(t) i s ergodic in both mean and autocorrelation. (8)
(ii) Write a short note on shot noise and also explain about power spectral density of shot noise. (8)
OR
13. (b) Write the details about narrow band noise and the properties of quadrature components of narrowband noise. (16)

14. (a) Derive an expression for SNR at input (SNRc) and output of (SNRo) of a coherent detector. (16)
OR
14. (b) (i) Explain pre-emphasis and De-emphasis in detail. (10)
(ii) Compare the performances of AM and FM systems. (6)

15. (a) (i) Find the code words for ¯ve symbols of the alphabet of a discrete memory-less source with probability f0.4, 0.2, 0.2, 0.1, 0.1g, using Hu®man coding and determine the source entropy and average code word length. (10)
(ii) Discuss the source coding theorem. (6)
OR
15. (b) (i) Derive the channel capacity of a continuous band limited white Gaussian noise channel. (10)
(ii) Discuss about rate distortion theory. (6)

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