# EC2305 TRANSMISSION LINES AND WAVEGUIDES NOVEMBER/DECEMBER 2010 ANNA UNIVERSITY QUESTION PAPER

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010

2. What are the advantages of m-derived filters?

3. Define delay distortion.

4. Write the expressions for the phase constant and velocity of propagation for telephone cable.

5. A lossless line has a characteristic impedance of 400 ohms. Determine the standing wave ratio if the receiving end impedance is 800 +j 0.0 ohms. 6. Write the expressions for the input impedance of open and short circuited dissipationless line.

7. Define the cutoff frequency for the guided waves.

8. For a frequency of 6 GHz and plane separation of 3 cm, find the group and phase velocities for the dominant mode.

9. Calculate the cutoff wavelength for the TM11 mode in a standard rectangular waveguide if a = 4.5 cm.

10. Give the applications of cavity resonators.

11. (a) (i) Design a m-derived T-section low pass filter having a cutoff frequency (fc) of 5000 Hz and a design impedance of 600 ohms. The frequency of infinite attenuation is 1.25 fc. (8)

(ii) Draw and explain the operation of crystal filters. (8)

(ii) Draw a constant-K T-section band elimination filter and explain the operation with necessary design equations. (8)

12. (a) (i) A transmission line has the following per unit length parameters : L = 0.1μ H, R =5 ohms, C = 300 pF and G = 0.01 mho. Calculate the propagation constant and characteristic impedance at 500 MHz. (8)

(ii) Derive the conditions required for a distortionless line. (8)

(ii) Explain the reflection on lines not terminated in characteristic impedance with phasor diagrams. Define reflection coefficient and reflection loss. (10)

13. (a) (i) Draw and explain the operation of quarter wave line. (8) (ii) It is required to match a 200 ohms load to a 300 ohms transmission line to reduce the SWR along the line to 1. What must be the characteristic impedance of the quarter wave transformer used for this purpose if it is directly connected to the load? (4)

(iii) What are the drawbacks of single stub matching and open circuited stubs? (4)

(ii) A UHF lossless transmission line working at 1 GHz is connected to an unmatched line producing a voltage reflection coefficient of 0.5(0.866 + j 0.5). Calculate the length and position of the stub to

match the line. (8)

14. (a) (i) Explain the transmission of TE waves between parallel perfectly conducting planes with necessary expressions and diagrams for the field components. (12)

(ii) A TEM wave at 1 MHz propagates in the region between conducting planes which is filled with dielectric material of r μ = 1 and r ε = 2. Find the phase constant and characteristic wave impedance. (4)

(ii) Write a brief note on the manner of wave travel and their velocities between parallel planes. (6)

15. (a) (i) Discuss the propagation of TM waves in a rectangular waveguide with relevant expressions and diagrams for the field components. (10)

(ii) A rectangular waveguide measuring a = 4.5 cm and b = 3 cm internally has a 9 GHz signal propagated in it. Calculate the guide wavelength, phase and group velocities and characteristic impedance for the dominant mode. (6)