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TRANSMISSION LINES AND WAVEGUIDES OCTOBER / NOVEMBER 2003.

All questions carry equal marks.

Answer Question No.1 Compulsorily. (1x14=14)

Answer One Question from each UNIT (4x14=56)

1. a) Define reflection coefficient?

b) What ist he conditions for distortion less transmission line?

c) A 150 lossless line is terminated in an impedance of j 30 . What is

the magritude of reflection coefficient?

d) Define insertion loss?

e) The parameters of a lossless line are L = 227 nH/m and C= 90.9p/F/m,

what is the oz

of the line?

f) A quarter wave long line is terminated in a short circuit. What is the sending

end impedance?

g) What is the distance at which the second wall may be placed, in a parallel

waveguide without disturbing the pattern created by first wall?

h) If the phase velocity in a guide is 5.43 x 810 m/s. What is the group

velocity?

i) Sketch the field distribution over the transverse plane of a rectangular guide

operating in the dominant mode.

j) A rectangular wave guide measures 3 x 4.5cm. What is the cut off

wavelength for the dominant mode?

k) What do the subscripts of the 21TE mode in a circular wave guide

represent?

l) The internal diameter of a circular waveguide is 4 cm. What is the cut-off

wavelength for 11TE mode?

m) What is the mode of wave propagation in a strip line?

n) Draw the field pattern in microstrip line?

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UNIT I

2. a) Derive expressions for and for a lossy line in terms of the primary

constants of the line.

b) A two wire line operating at 5 kHz has 0z = 600 j2.0 and y = 3.37 x

47 1005.110 + xj per m. Compute the primary constants of the line.

Or

3. a) Show that V =Vo exp ( 1y ); where y = j+ , satisfics the transmission

line equation.

b) Derive expressions for and of a lossy line in terms of the primary

constants of the line.

UNIT II

4. a) Derive an expression for the sending end impedance of a loss- less line.

b) Derive conditions for distortionless transmission line. How it is achieved.

Or

5. a) A 50 transmission line is connected to a load of 25- j50 . Find all

possible positions and lengths of a short circuited stub required to match the

load to the line using Smith Chart.

UNIT III

6. a) Explain clearly why it is not possible for a TEM wave to propagate in a

hallow rectangular waveguide.

b) A rectangular waveguide is operated at 12 GHz in the dominant mode such

that = 450 . What must be the corresponding cross-section

dimensions of the guide?

Or

7. a) What is the difference between attenuation for and in a

waveguide? With relevant expressions, give procedure calculating the

attenuation constant for in a rectangular waveguide.

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b) A waveguide has dimensions of 3 cm breadth and carries the dominant

mode of a signal of unknown frequency. If the characteristic wave

impedance is 500 , what is this frequency?

UNIT IV

8. a) Derive expressions for TE component in terms of longitudinal field

components of a circular waveguide.

b) Calculate the 0,, andzf gc of circular waveguide whose internal diameter is

4 cm, for a 10 GHz signal propagated in the dominant mode.

Or

9. a) Write short note on strip lines.

b) Calculate the ratio of the cross sectional area of a circular waveguide to

that of a rectangular one if each is to have the same cut-off wavelength for

its dominant mode.