# TRANSMISSION LINES AND WAVEGUIDES EC2305 NOVEMBER/DECEMBER 2010 ANNA UNIV PREVIOUS YEAR QUESTION PAPER

*r*Î¼ = 1 and

*r*Îµ = 2. Find the phase constant and characteristic wave impedance. (4)

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

Fifth Semester

Electronics and Communication
Engineering

EC 2305 — TRANSMISSION LINES AND
WAVEGUIDES

(Regulation 2008)

Time : Three hours Maximum : 100 Marks

Answer ALL questions

PART A — (10 × 2 = 20 Marks)

1. A constant-K T-section high pass filter has a cutoff
frequency of 10 KHz. The design impedance is 600 ohms. Determine the value of
L.

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.

PART B — (5 × 16 = 80 Marks)

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)

Or

(b) (i) Design a constant-K T-section bandpass filter with
cutoff frequencies of 1 KHz and 4 KHz. The design impedance is 600 ohms.

(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 = 0.1Î¼ 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)

Or

(b) (i) The characteristic impedance of a uniform
transmission line is 2309.6 ohms at a frequency of 800 MHz. At this frequency,
the propagation constant is 0.054(0.0366 + j 0.99). Determine Rand L.

(6)

(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)

Or

(b) (i) Draw and explain the principle of double stub
matching. (8)

(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 *Î¼ = 1 and *r *Îµ = 2. Find the phase constant and
characteristic wave impedance. (4)

Or

(b) (i) Explain the reasons for the attenuation of TE and TM
waves between parallel planes with necessary expressions and diagrams. (10)

(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)

Or

(b) Explain the propagation of electromagnetic waves in a
cylindrical waveguide with suitable expressions.(16)

TRANSMISSION LINES AND WAVEGUIDES EC2305 NOVEMBER/DECEMBER 2010 ANNA UNIV PREVIOUS YEAR QUESTION PAPER
Reviewed by Rejin Paul
on
6:47 AM
Rating: 5

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