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# 2007 SRM University B.Tech. Electronics and Communications Engineering QUESTION BANK FOR Transmission Lines and Wave Guides Question paper

 Course: B.Tech. Electronics and Communications Engineering University/board: SRM University

S.R.M. Institute of Science & Technology
School of Electronics & Communication Engineering
QUESTION BANK
Subject Code : EC206
Subject Name : Transmission Lines and Wave Guides
Year & Sem : II Year , 4th Sem (ECE)
UNIT I – TRANSMISSION LINE THEORY
PART-A

1. What are the different types of transmission lines?
2. Draw the equivalent circuit of transmission line.
3. What are the primary and secondary constants of transmission lines?
4. Write Characteristic Impedance and Propagation Constant interms of Primary Constants of line.

5. Define Infinite Line.
6. Write the General Line equation of a transmission line.
7. Write Input Impedance of open and short circuit line.
8. Why Reflection occurs in Transmission lines?
9. Define Reflection loss.
10. Define Reflection Coefficient.
11. Define Reflection Factor.
12. Define Waveform Distortion and mention its types.
13. Define Frequency Distortion.
14. Define Phase or Delay Distortion.
15. What is the condition for Distortion less line?
16. What is smooth line?
20. What is Transfer Impedance and write its Equation.
21. Write the relation between Zo, Zoc & Zsc.
22. An Open wire Telephone Line has R=10 ohms/Km, L=0.0037H/Km, C=0.0083 micro Farad/Km and G=0.4 micro mhos/Km. Determine Zo at 1000Hz.

23. If Zoc=710/_50 ohms , Zsc=300/_80 ohms. Find Zo.
24. A 100 Km long Transmission Line is terminated by a resistance of 200 ohms. Zo=600 ohms. Find the reflection Coefficient.
PART-B
1. Derive the General Line Equation of a Transmission Line.
3. Find the sending end impedance of line having negligible losses, where Zo is 55 ohms and receiving end impedance 155+j75 ohms and line is 1.183 times the Wavelength.

4. a) Explain the reason for reflection and derive an equation for Reflection Coefficient. b) Explain Reflection and derive the equation for reflection factor and reflection loss.

5. Explain about different types of distortion and derive the condition for distortion less line.

6. The primary Constants of a cable are R=80 ohms/Km, L= 2mH, G= 0.3 micro mhos/Km and C= 0.07 micro Farad/Km. Calculate the Secondary Constants and the velocity of propagation at 100Hz.

7. a)Derive the equation of Input Impedance and Transfer Impedance of a Line
b) In a Line per kilometer R=42.9 ohms, L=0.07 mH, C=0.01 micro Farad and G=2.5 micro mhos. Find the Characteristic Impedance when w=5000 rad/sec.

8. A long transmission line of characteristic Impedance 500/_-43 ohms and Propagation Constant of 0.07+j0.08 per Km is properly terminated. A voltage of 5V is applied at the sending end. Calculate the voltage and current at a distance of 10 km from the receiving end.

9. A 50 mile line has the following measurements . Zoc=200/_-42 ohms, Zsc=1890/_22 ohm Find the value of Zo, a, ß, v(velocity) for this line if the frequency is 1200 Hz.

UNIT-II - TRANSMISSION LINES AT HIGH FREQUENCIES
PART-A
1. Write the assumptions that are made at high frequencies or at radio frequencies for a transmission line.
2. What is meant by a Zero dissipation line?
3. Write down the expressions for the characteristics impedance and propagation constant of a line at radio frequencies.
4. Write the voltage and current equation of a zero dissipation line .
5. What is meant by Standing Waves?
6. Define Nodes and Anti Nodes.
7. Draw the Standing Wave Pattern for a line which is terminated with a load not equal to Ro.
8. Draw the Standing Wave Pattern for a line which is terminated with i) open and ii) short circuit termination.
9. Define Standing Wave Ratio.
10. Write the Input Impedance equation for a dissipation less line.
11. Write the minimum & maximum value of Impedance of a zero dissipation line.
12. Write the Input Impedance equation for a zero dissipation line with i) open and ii) short circuit termination.
13. Draw the variation of Impedance of dissipation less line as a function of length for a line with Short circuit termination.
14. Draw the variation of Impedance of dissipation less line as a function of length for a line with Open circuit termination.
15. Write the Power equation for a dissipation less line.
16. If the load Impedance is 54-j74 ohms and Zo =150 ohms, find the Standing Wave Ratio.
17. A HF line has following primary constants L=1.2mH/km, C=0.05microFarad/km and is operated at 1MHz. Determine Zo and ?.
18. A Lossless line having Zo = 50 ohms and terminated in a load ZR and VSWR on the line is. Calculate maximam and minimum values of impedance along the line.
19. Give the relation between VSWR and Reflection Coefficient.
20. If the VSWR of a particular Transmission line is 2.5, then calculate the magnitude of the reflection coefficient.

PART-B
1. a) Explain about Zero Dissipation Line and derive the equations for characteristic impedance, propagation constant and velocity of propagation.
b) Derive the expressions for voltage and Current at any point on a line at Radio Frequency terminated in ZR.
2. a) Explain about Standing Waves .Draw the Standing wave pattern for i) Open circuit load, ii) Short Circuit Load and iii) Matched Load.
b) Draw the impedance variation of open and short circuited RF line.
3. Explain the method of Power and Impedance measurement on a zero dissipation Line.
4. Explain how Standing Wave Ratio and Wavelength can be measured in a transmission line.
5. An UHF Transmission line of Zo=75/_0 ohms is terminated in an unknown load. The VSWR measured in the line is 3 and the position of voltage minima nearest to the load is one fifth wavelength away from the load. Calculate the value of load Impedance, VSWR.
6. The terminating load of UHF transmission line (Zo=50/_0 ohms) working at 300 MHz is 50+j50 ohms. Calculate the VSWR and the position of the voltage minimum nearest the load.
7. A lossless 100 Ohms transmission line is terminated in 200 +j200 Ohms . Find a) Voltage reflection coefficient b) VSWR c) Impedance 0.375? from load
UNIT – III IMPEDANCE MATCHING AT HIGH FREQUENCIES
PART-A
1. Give the expression for input impedance of a quarter wave line ?
2. What will be the characteristic impedance of a quarter wave lines to match two transmission lines having characteristic impedance of 100,75 ?
3. What are the applications of quarter wave line?
4. What is a stub?
5. What are the advantages of stub matching?
6. What are the types of stub matching?
7. Mention the need for impedance matching.
8. What are the disadvantages of single stub matching?
9. What is normalization of impedance?
10. What is smith chart? What is the distance around smith chart?
11. What are the two set of circles in smith chart and mention its center and radius.
12. What is the significance of R=1 circle in the smith chart?
13. What is the centre and radius for constant resistance circle?
14. What is the centre and radius for constant reactance circle?
15. What are the applications of smith chart?`
16. What is the distance between Imax & Imin and Vmax & Vmin?

PART-B
1. A transmission line of characteristic impedance Zo is terminated by ZR, derive the expression for the position of attachment and length of a short circuited stub.

2. Explain about the features and applications of Smith Chart.
3. (i) Give detail explanation about the quarter wave transformer
(ii) Explain about double stub matching in detail.

4. A low loss line with Zo = 70 ohms is terminated in an impedance ZR=115-j80 ohms. using smith chart find the following:
i. Standing wave ratio
ii. Maximum and Minimum line impedance
iii. Distance between the load and first voltage minimum

5. Determine the length and location of the stub to produce an impedance match on a line of Ro = 600ohms terminated in 200 ? 0o ohms. The stub is short circuited at the other end. Verify result using Smith chart.

6. A transmission line 52 cm long has a characteristic impedance of 50 ohms. It is terminated in a load of ZR. The VSWR is 2.5. The first voltage minima occur at 18cm and 2nd voltage minima 38cm from the load end. Using smith chart, determine ZR and input impedance of the line.

7. An R.F. transmission line with a characteristic impedance of 300? 0o is terminated in an impedance of 100 ?45o ohms. This load is to be matched to the transmission line by using a short circuited stub. With the help of a Smith chart determine the length of the stub and its distance from the load.

8. A transmission line has a characteristics impedance of 300 ? and terminated in a load 150 +j150? . Find the following using Smith Chart. a) VSWR b) Reflection coefficient
c) Impedance at a distance of 0.1? from the load. d) Position of first voltage minimum from the load.

9. For a load 25 + j50 design a double stub tuner making the distance between stubs ?/8. The distance between the 1st stub and load is ?/4. Assume Z0=50?

UNIT – IV GUIDED WAVES AND WAVEGUIDES
PART-A

1. Distinguish between transverse electric and transverse magnetic waves
2. Distinguish between phase velocity and group velocity
3. Give the expression for cut-off frequency for TE Mode.
4. What is the cut-off wavelength for the TE10 mode?
5. Define Guide Wavelength.
6. What is phase velocity?
7. Why is the dominant mode of propagation preferred with rectangular Wave Guide.?
8. State any two characteristics of TEM waves.
9. What is a waveguide?
10. What are the transverse electric (TE) Waves?
11. What are the transverse magnetic (TM) Waves?
12. Find the frequency of minimum attenuation for TM mode.
13. Define dominant mode in a Wave Guide.
14. Write down the relation between guide wavelength, free space wavelength and Cut-off wavelength.
15. For the TM mode between parallel planes, Write down an expression for the frequency at which the attenuation is a minimum.
PART-B

1. A 4GHZ signal is propagated in a rectangular Wave Guide with internal dimensions of 5 X 2.5 cm. Assuming the dominant mode, Calculate.
a) Cut-off wavelength b) Guide Wavelength
c) Group Velocity d) Phase Velocity
2. Obtain the field components of the wave propagating between parallel planes.
3. Derive the EM field expression for TM Waves guided by a parallel plane perfectly conducting structure.
4. Derive the field expressions for TE Waves guided by a parallel plane perfectly conducting structure.
5. Deduce expression for propagation Constant, Wavelength and Velocity of propagation for TE waves between parallel planes.
6. Discuss the propagation of TM waves in a rectangular Wave Guide. Derive the general relationship which connects free space wavelength, guide wavelength and critical wavelength.
7. An air filled hollow rectangular Wave Guide has cross-sectional dimensions 12cm X 9cm. Find the cut off frequency for the following modes:
i)TE10, TE11, and TE21.
ii) Explain why it is not possible to propagate a TEM wave inside a hollow Wave Guide of any cross section?

UNIT – V WAVEGUIDE TECHNOLOGY
PART-A

1. Differentiate between Transmission Lines and Wave Guides.
2. What is the need for coupling in waveguides?
3. Why is slot provided in Wave Guide?
4. What is directional Coupler?
5. How do you suppress the unwanted modes?
6. What is the purpose of resonant obstacles in Wave Guides.?
7. State the function of directional Coupler?
8. What are called unwanted modes in a Wave Guide?
9. Mention two applications of Wave Guide directional Couplers?
10. What is the purpose of mode filter?
PART-B

1. Explain in detail, the generation of different Wave Guide modes.
(a)Describe the different modes of impedance matching in Wave Guides.
(b)How do you suppress the unwanted modes? Explain.

2. Write a short notes on
a) Directional Coupler b) Resonant Obstacles in Wave Guide

3. Discuss in detail the field distributions and SWR in waveguide
4. Explain the following
i) Coupling and leakage through slots and holes in Wave Guide walls.
ii) Reflected and Incident Waves and SWR in Wave Guide.

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