GITAM University 2005 B.E Electronics & Tele-Communication Engineering Transmission Lines & Waveguides - Question Paper

College of Engineering
Gandhi Institute of Technology and Management, Visakhapatnam
(Affiliated to Andhra University)

B.E. (Electronics and Communications Engineering ) 2nd Year
Second Semester exams 2004-2005
(Autonomous Stream)

EC 226 Transmission Lines & Wave guides

Time: three Hours Max. Marks: 60

1. Answer ques. No. one ( Part – A) and any 4 of the remaining 7 (Part – B)
2. All parts of a ques. must be answered in 1 place, otherwise they will not be valued.
3. Figures in the right hand margin indicate marks allotted.


Note : If in the provided paper if Z is followed by brackets (),it denotes the suffix of Z .


PART – A

1. Answer the subsequent. 10x2=20

a) What are primary constants of a transmission line?
b) If a line is terminated in its Z(0), it is electrically and infinitely long line. Why?
c) Define input impedance in terms of Z(0) and Z(R). Specify its value for open circuit and short circuit lines.
d) What is basically Smith Chart? On what plane it is drawn?
e) What is TEM mode? In what structures of guide this mode can exist.
f) Mention 2 kinds of power losses in rectangular wave guide.

g) Mention the various coupling methods that are used in circular wave guides briefly.
h) What is property of 1/4 and 1/8 lines if the line is lossless?
i) What is Cavity Resonator? Sketch the standing wave trend in a short circuited rectangular wave guide.
j) Distinguish ranging from strip line and microstrip line in terms of E field trend with a neat sketch.


PART – B

ans any 4 of the subsequent. If you attempt more than 4 questions, only the 1st 4 in order will be valued.

2.
a) Derive expressions for a and ß for telephone cable. (5)

b) A generator of one volt, 1000 Hz supplies power to 1000 Km long open wire line terminated in characteristic impedance Z0 and having subsequent parameters.
R = 10.4 Ohms L = 0.0037 henry
G = 0.8 micromhos C = 0.00835 microfared
compute phase velocity, characteristic impedance, propagation constant, attenuation constant and phase constant. (5)

3.
a) Derive equivalent T network of a transmission line having propagation constant and characteristic impedance Z(0). (5)

b) For a transmission line, VSWR is 1.5, the characteristic impedance is 100 ohms and the line is to transmit a power of 50 watts. compute the magnitudes of maximum and minimum voltage and current. Also obtain magnitude of receiving end voltage. provided receiving end impedance (ZR) = 150 ohms. (5)

4.
a) What is stub matching? Distinguish ranging from single stub and double stub matching with a neat sketches. (6)

b) Compute input impedance of (i) Quarter wave transformer (ii) Half wave transformer if Z0 = 100 ohms, ZR = 200 ohms. (4)

5.
a) Determine reflection coefficient and VSWR for the following:
i) Z(L) = Z(0) (ii) Z(L) = 0 (iii) Z(L) = 1/0
(iv) Z(L) = Z(0)/2 (vi) Z(L) = two Z(0)


b) Explain the construction of Smith Chart and illustrate the different applications of Smith Chart. (5)

6.
a) Distinguish ranging from TE and TM modes in a guide. (3)

b) Prove that TEM mode can not propagate through single conductor guide. (3)

c) A rectangular wave guide of cross part five cm x three cm is used to propagate TM11 mode at nine GHz. Determine the cut off wavelength and wave impedance. (4)

7.
a) Obtain the field formula of TM mode in circular wave guide. (5)

b) A TE11 wave is Propagated through a air filled circular wave guide of diameter 10 cm. Determine i) the cut off frequency ii) guide wave length for a frequency of three GHz. iii) wave impedance of the guide. (5)

8. Write short notes on any 2 of the subsequent. (2x5=10)
a) Phase and group velocities of wave.
b) Advantages and disadvantages of Microstrip lines.
c) Cavity resonator.

Earning:   Approval pending.