QUESTION BANK DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING TRANSMISSION LINES AND WAVEGUIDES

VINAYAKA MISSIONS UNIVERSITY

V.M.K.V ENGINEERING COLLEGE, SALEM

 

QUESTION BANK

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

TRANSMISSION LINES AND WAVEGUIDES

UNIT I

PART A

1. Define Characteristic impedance.
2. Define Propagation constant.
3. What is a finite line? Write down the significance of this line?
4. What are the types of line distortions?
5. How to avoid the frequency distortion that occurs in the line?
6. What is a distortion less line? What is the condition for a distortion less line?
7. What is the drawback of using ordinary telephone cables?
8. What is loading?
9. What is patch loading?
10. Define reflection coefficient.
11. When reflection occurs in a line?
12. What are the conditions for a perfect line? What is a smooth line?
13. List the parameters of a transmission line?
14. State the conditions for a distortion less line.
15. Define phase velocity and group velocity.
16. What are the disadvantages of parallel open wire line?
17. What do you mean by loading of transmission line?
18. What is the principle of reflection phenomenon?
19. Why is waveform distorted in transmission line?
20. A transmission line with a characteristic resistance of 50 ohm is connected to a 100-ohm resistance load. Calculate the voltage reflection coefficient at the load.
21. Mention the characteristics of an infinite line.
22. Write a note on i) Reflection loss ii) Insertion loss.
23. What are the practical considerations of underground cable?
24. Write a note on Telephone cable.
25. What is return loss?

PART B

1.      i) Develop the differential equations governing the voltage and current at any point on a        uniform transmission line, and then solve these to obtain the voltage and current in terms of the load current and voltage.

ii) Explain physical significance of a general solution of transmission line.

2.      i) Derive the equations of attenuation constant and phase constant of a transmission line in terms of the line constants R, L, C and G.

ii) A generator of 1 V, 1 KHz supplies power to a 100 km open wire line terminated         in 200 Ω resistance. The line parameters are R = 10 Ω/ Km, L = 3.8 mH / Km, G = 1 x 10 ^-6 mho/ Km, C = 0.0085 uF/ Km.

Calculate the input impedance, reflection coefficient and sending end current.

3.      i) Show that a line will be distortion less if CR = LG.

ii) A transmission line has the following per unit length parameters

R = 52 Ohm/m, L = 0.1 uH / m, C = 300 pF / m, G = 0.01 mho/m

Calculate the propagation constant and characteristics impedance of transmission line at 500 MHz; obtain the same parameters for loss less line.

4.      i) Derive the expression for input impedance and transfer impedance interms of Z_O,   Z_R and propagation constant p.

ii) Derive the expression for α and β for continuous loading also list out its advantages and disadvantages.

5.      i) Derive the expression for the insertion loss of transmission line.

ii) A transmission line has Z_{O =}700∟-13.4^o ohm is inserted between a generator of 200 ohm and a load of 400 ohm. The attenuation and phase constant of                         the line is α = 0.00712 neper / Km and β = 0.0288 rad / Km. Calculate the insertion loss if the length is 200 Km.

6.      What is lumped loading? Derive Campbell’s equation for lumped loading.

7.      Describe the expression of a line not terminated in Z_0.

8.      Derive the expression for insertion loss on a line.

9.      A transmission line of 2 miles long operates at 10 kHz and has parameters R=30 Ω/mile, L=2.2mH/mile, C=80nF/mile and G=20nV/mile. Find the characteristic impedance, propagation constant, attenuation and phase shift per mile.

10.  Find the sending end impedance of the line having Z_o=710∟14^o, υ=0.007+j0.028/km,Z_R=300 ohm, l=100 km.

UNIT II

PART A

1. State the assumptions for the analysis of the performance of the radio frequency line.
2. State the expressions for the capacitance of   an open wire line.
3. What are nodes and antinodes on a line?
4. What is the range of values of standing wave ratio?
5. What is called standing wave ratio?
6. How will you make standing wave measurements on coaxial lines?
7. Give the input impedance of dissipationless line.
8. What is the application of the quarter wave matching section?
9. Explain impedance matching using stub.
10. Give the formula to calculate the length of the short circuited stub.
11. List the applications of the smith chart.
12. What are the difficulties in single stub matching?
13. Give reason for an open line not frequently employed for impedance matching.
14. Why Double stub matching is preferred over single stub matching.
15. What are small dissipation line and zero dissipation line?
16. Draw the sketches showing variations of input impedance of a short circuited dissipation less line as a function of wave length.
17. Define standing wave ratio.
18. Write the expression for input impedance of RF line.
19. What is the condition for a line to have zero dissipation?
20. A 50 ohm line is terminated in load Z_R (90+j60). Determine VSWR due to this load.
21. Draw a net sketch of variation of input impedance of an open circuited dissipation less line.
22. Write down the expression for the voltage at a point S away from the receiving end interms of reflection coefficient.
23. List out the approximations be employed for simplified analysis of line performance at radio frequencies.
24. Distinguish between nodes and antinodes.
25. A line with characteristic impedance of 692∟-12º is terminated  with 200 ohm resister. Determine K.

PART B

1. Discuss how a smith chart is constructed and explain its applications.
2. Explain the following:

      i) Single stub matching.          ii) Double stub matching.

3. Derive the expression of circle diagram for the transmission line.
4. A dipole antenna whose input impedance is 100 ohm is to be matched at frequency of 100 MHz to a transmission lines having Z_o of 600 ohm   by means of short circuit stub. Determine the location and length of the stub.
5. Determine the SWR, characteristic impedance of the quarter wave transformer, and the distance the transformer must be placed from the load to match a75 ohm , transmission line to load Z_L=25-j50 ohm.
6. Determine the input impedance of open and short circuited dissipationless transmission line.
7. Explain about one eighth wave line and quarter wave line.
8. Define and explain the following

i)        Standing waves

ii)      Standing wave ratio

iii)    Relation between SWR and ‘K’.

iv)    A method to measure SWR.

9. Discuss the measurement of power and impedance on transmission line using phasor diagrams.
10. Explain the method of measurement of standing wave ratio  in open wire line.

UNIT III

PART A

1. What are guided waves? Give examples.
2. What is cut off frequency?
3. Mention the characteristics of TEM waves.
4. Define attenuation factor.
5. Give the relation between the attenuation factor for TE waves and TM waves
6. Why are rectangular wave-guides preferred over circular wave-guides?
7. Mention the applications of wave guides.
8. What is a TEM wave or principal wave?
9. What is TH wave or E wave?
10. Distinguish TE wave and TM wave?
11. What is a principal wave?
12. Give the dominant mode for TE and TM waves
13. Mention the characteristics of TEM waves.
14. What are micro strip lines?
15. What are the losses associated with microstrip line?
16. What are the disadvantages of micro strip lines?
17. What is a parallel plate wave guide?
18. What is a wave-guide?
19. Write the properties of TEM waves.
20. Write the point form of Maxwell’s equation.
21. Write the condition of good conductor.
22. Write the integral form of Maxwell’s equation.
23. A pair of perfectly conducting planes is separated 4 cm in air. For a frequency of 5000 MHz with TM₁ mode, find cut off wavelength.
24. Write the differential form of Maxwell’s equation.
25. For a frequency of 6000 MHz and plane separation of 7 cm, find critical wavelength.

PART B

1. Derive the electromagnetic field expressions for waves guided by a parallel conducting plane?
2. (i) Bring out the differences between  TE,TM and TEM waves.

(ii) Find the cut-off frequency for the TE₁ mode for the frequency of 6000 MHz and plane separated by 7 cm.

3. Derive an expression for attenuation factor for TEM waves in two parallel conducting planes.
4. Define wave impedance. Obtain the expression for wave impedance of TE, TM and TEM waves in two parallel conducting planes.
5. Explain about the velocity propagation of guided waves..
6. Derive the expressions for the field components of TM waves in a parallel plane waveguide.
7. For the frequency of 6000 MHz and plane separation of 7 cm, find the following for TE₁ mode.

i)        Critical frequency

ii)      Phase constant

iii)    Attenuation constant

iv)    Critical wavelength.

8. Write the properties of TEM waves. Write different characteristics of TE and TM waves.
9. Discuss the characteristics of TE and TM waves and also derive the cutoff frequency and phase velocity from the propagation constant.
10. A parallel plane waveguide with plate separation of 20 cm with TE₁ mode excited at 1 GHz. Find the phase constant.

UNIT IV

PART A

1. Why is rectangular form used as waveguide?
2. What is the dominant mode for the TE waves in the rectangular waveguide?
3. What is the dominant mode for the TM waves in the rectangular waveguide?
4. Which  are  the  non-zero  field  components  for  the  TM11   mode  in  a rectangular waveguide?
5. Define characteristic impedance in a waveguide.
6. Explain why TM01 and TM10 modes do not exist in a rectangular waveguide?.
7. What are degenerate modes in a rectangular waveguide?
8. What is the dominant mode for the rectangular waveguide?
9. What is a wave-guide?
10. Mention the applications of wave guides.
11. Why is circular or rectangular form used as waveguide?
12. What is the dominant mode for the rectangular waveguide?
13. Which are the non-zero field components for the TE₁₀ mode in a rectangular waveguide?
14. Which are the non-zero field components for the TM₁₁ mode in a rectangular waveguide?
15. Define characteristic impedance of rectangular waveguide.
16. Why TEM mode is not possible in a rectangular waveguide?
17. Why TM₀₁ and TM₁₀ modes in a rectangular waveguide do not exist?
18. Write the boundary conditions in rectangular wave guide.
19. Define cutoff wavelength.
20. Draw the field pattern for TE₁₁ mode.
21. Find λ_c for a standing rectangular wavelength for TE₁₁ mode
22. Define the phase velocity and group velocity.
23. A rectangular wave guide has the following dimensions l = 2.54 cm, b = 1.27 cm wavelength thickness = 0.127 cm. Calculate the cutoff frequency for TE₁₁ mode.
24. What are degenerate modes in rectangular waveguide?

PART B

1. Derive the expressions for the field components of TM waves in a rectangular waveguide.
2. Derive the expressions for the field components of TE waves in a rectangular waveguide.
3. Derive an expression for attenuation factor in a rectangular waveguide for TE and TM waves.
4. Explain how various modes can be excited in a rectangular waveguide.
5. Derive an expression for wave impedance for TE and TM waves in rectangular waveguide.
6. Explain the characteristic impedance of a rectangular waveguide and derive the expression for TE, TM and TEM waves.
7. When the dominant mode is propagated through a wave guide at a frequency of 9 GHz the wavelength is found to be 4 cm. Find the dimension of breadth  of the guide.
8. The cutoff wavelengths of a rectangular waveguide are measured to be 8 cm and 4.8 cm for TE₁₀ and TE₁₁ modes respectively. Determine Waveguide dimensions.
9. Briefly explain the transmission line and wave guide.
10. Discuss the attenuation of Electromagnetic wave guide along rectangular waveguide.

UNIT V

PART A

1. What is a circular waveguide?
2. Why circular waveguides are not preferred over rectangular waveguides?
3. Mention the applications of circular waveguide.
4. What are the possible modes for TM waves in a circular waveguide?
5. Mention the dominant modes in rectangular and circular waveguides.
6. What are the possible modes for TE waves in a circular waveguide?
7. What is the dominant mode in a circular waveguide?
8. What are the performance parameters of microwave resonator?
9. Define quality factor of a resonator.
10. When a medium is said to be free- space?
11. What is the dominant mode for TE waves in a circular waveguide?
12. What are the root values for the TM modes?
13. Write down the expression for the wave impedance of TM waves in circular wave guide.
14. Define Q of a wave guide.
15. Write the attenuation factor for TE₁₀ mode in circular wave guide.
16. Why is TM₀₁ mode preferred to the TE₀₁ mode in a circular waveguide?
17. Write the note on excitation of waveguides.
18. Draw the field patterns for the dominant mode of TE_mm wave in the circular waveguide.
19. How the TE₁₀ mode is launched in rectangular waveguide using a probe?
20. Which is the most dominant mode in rectangular waveguide? Why?
21. What is the Bessel’s function?
22. Write the note on guide terminations.

PART B

1.      Derive the expressions for the field components of TM waves in a circular waveguide.

2.      Derive the expressions for the field components of TE waves in a circular waveguide.

3.      Derive an expression for attenuation factor in a circular waveguide for TE and TM waves.

4.      Explain the various methods of excitation modes in circular wave guide.

5.      Discuss about the wave impedance in circular wave guide.

6.      Given the circular waveguide of internal diameter 12 cm operating with a 8 GHz. Signal propagating TM₂₂ mode. λ₀, λc, and λg.

7.      Determine the solution of electric and magnetic fields of TM waves guided along circular waveguide.

8.      Derive TM wave components in circular waveguides using Bessel function.

9.      Derive the cutoff frequency, phase shift constant and velocity of propagation of waves in a circular waveguide.

10.  A cylindrical copper tube of diameter 3 cm is air filled. Calculate cutoff frequencies in TE₀₁, TM_01, TE₁₁ and TM₁₁ modes.