# 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.