02-11-2012, 05:44 PM

Anna university

B.E / B.TECH. DEGREE EXAMINATION,MAY/JUNE 2009.

Dept. : ECE

3rd yr

Fifth Semester

(Regulation 2004)

EC 1305-TRANSMISSION LINES AND WAVEGUIDES

Answer All Questions

PART A-[10 x 2 = 20]

1.What is propagation constant ? Which are its two components?

2.State the condition for distortionless line.

3.If the reflection co-efficient of a line is 0.3 ?_?-66?^° ¦ ,calculate the standing wave ratio.

4.What is the value of Z_° for the dissipationless line?

5.What are the characteristics of TEM wave?

6.Write Maxwell’s equations in point form.

7.A rectangular waveguide with dimensions a=8.5cm and b=4.3cm .Determine the cut-off frequency for ?TM?_10 mode of propagation.

8.What is meant by dominant mode of the wave?

9.What is meant by cavity resonator?

10.What is the dominant mode in circular waveguide ? Why ?

PART B-[5 x 16 = 80]

11.(a)(i) Derive the expression for voltage and current at any point on a transmission line in terms of receiving end voltage and current.[Marks 10]

11.(a)(ii) A line has the following primary constants

R=100 ?/km L=0.001 H/km

G=1.5 µv/km C=0.062 µF/km.

Find the characteristic impedance and the propagation constant .[Marks 6]

(or)

11(b)(i) Derive Campbell’s equation.[Marks 8]

11.(b)(ii) A generator of 1V,1kHz supplies power to a 100km transmission line terminated in 200 ? resistance. The line parameters are R=10?/km, L=3.8 mH/km, G=1µv/km, C=0.0085 µF/km Calculate the input impedance and reflection coefficient.[Marks 8]

12(a)(i)Define standing wave ratio and obtain the expression of VSWR in terms of reflection coefficient.[Marks 8]

12.(a)(ii) Derive the input impedance of a quarter wave line and discuss its applications.[Marks 8]

(or)

12.(b)(i) Obtain the length and the location of a short circuited stub for impedance

matching on a transmission line.[Marks 10]

12.(b)(ii) A load (50-j100)? is connected to a 50? line. Design a short circuited stub to provide matching between the two at signal frequency of 30Mhz using Smith Chart.[Marks 6]

13.(a)(i) Obtain the solution of field components of a TE wave between parallel plate , propagating in Z direction.[Marks 10]

13.(a)(ii)A pair of perfectly conducting planes are separated by 3.6cm in air. For ?TM?_10 mode determine the cut-off frequency and cut-off wavelength, if the operating frequency is 5Ghz.[Marks 6]

(or)

13.(b)(i) Derive the expressions for the field components of TEM waves between parallel conducting planes. Discuss the properties of TEM waves.[Marks 10]

13.(b)(ii)For a frequency of 10 GHz and plane separation of 5cm in air, find the cut-off wavelength, phase velocity and group velocity of the wave.[Marks 6]

14(a) Deduce the expressions for the field components of TM waves guided along rectangular waveguide. [Marks 16]

(or)

14.Derive the expression of wave impedance for TE and TM waves guided along rectangular waveguide.[Marks 8]

14.(b)(ii) A ?TE?_10 mode is propagated through a waveguide with a=10cm at a frequency of 2.5Ghz.Find the cut-off wavelength, phase velocity, group velocity and wave impedance.[Marks 8]

(or)

15.(a)(i) Derive the expressions for the field components of TE waves guided along circular waveguide.[Marks 10]

15.(a)(ii) A circular waveguide has an internal diameter of 6cm.For a 9GHz signal propagated in the ?TE?_11mode,calculate the cut-off frequency and the characteristic impedance [?(ha)?_11^1=1.84].[Marks 6]

(or)

15.(b)(i)Obtain the expression for the resonant frequency of a rectangular cavity resonator.[Marks 8]

15.(b)(ii) Calculate the lowest resonant frequency of a rectangular cavity resonator of dimension a=2cm, b=1cm and d=3cm.[Marks 8]

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