Anna University Chennai 2006-1st Sem B.E Electronics & Tele-Communication Engineering VESTER fo EC342 - ELECTROMAGNETIC WAVES AND WAVE GUIDES - Question Paper

ANNA UNIVERSITY :: CHENNAI – 600 025
MODEL ques. PAPER
VI SEMESTER
B.E. ELECTRONICS AND COMMUNICATION ENGINEERING
EC342 - ELECTROMAGNETIC WAVES AND WAVE GUIDES
Time: 3 Hours Maximum : 100 Marks
ans All The ques.
PART – A (10 x two = 20 Marks)
1. Consider a parallel plate waveguide formed by conductors covering the planes y =
0 and y = b. Show that the field Ex = Eo Sin(npy/b)e -?z, n = 1,2,3 describes a set of
TEn modes.
2. Show that an uniform plane wave passing in any direction does not have any
component at that direction.
3. describe velocity of propagation of energy and show that for a uniform plane
traveling wave it is equal to its phase velocity.
4. Plane traveling wave reflected by dielectric on imperfectly conducting boundaries
will outcome in partial standing waves with SWR’s ranging from 1 and infinity. Justify.
5. Show that in lossy matter, a traveling wave is attenuated in the direction of travel
and ? is no longer in phase with ?.
6. describe clearly dominant and degenerate modes with examples.
7. Sketch the cross-sectional rectangular waveguide mode trend for TE10, TE11 and
TM11 modes with explanation and indicate the methods of excitation.
8. discuss why TEM wave is not possible in a hollow waveguide.
9. find the general expression for the mode chart formula for a cylindrical cavity.
What is its usefulness?
10. Show that for metals
? = R s (1+j), k = 1/d (1-j) and R s = one / s d
where R s is the surface resistance, d is the skin depth and s is the conductivity.
PART – B (5 x 16 = 80 Marks)
11. Derive the general expressions for all the field components existing in TE wave in
a rectangular waveguide (a > b) and discuss that it behaves like a high pass filter.
12.a) discuss various polarizations of electromagnetic waves and express them in
terms of mathematical models.
(OR)
12.b) Derive the expression for reflection Co-efficient for vertical polarization when a
wave is incident on a plane dielectric interface ranging from 2 media. What
phenomenon is of particular interest for this case.
13.a) Show that the Q factor of a rectangular waveguide cavity (a x b x d) excited in
dominant mode is provided by :
(koad)3 b Zo
Q = --------------------------------------------------
2p2 R s ( 2a3 b + 2d3 b + a3 d + d3 a)
where ko is the free-space propagation constant, R s is the surface resistance of
metal walls.
(OR)
13.b) Determine the range of radius of a circular waveguide filled with air so that only
dominant mode can be propagated at 10 GHz. Draw the field configuration of
dominant mode and discuss how such is excited.
14.a) The electric field strength of a uniform plane waves in free space is one V/m; at 300
MHz. If a very large thick flat copper plate is placed normal to the direction of
wave propagation, determine.
(i) E and H at the surface of the plate (ii) skin depth
(iii) the conduction current density at the surface
(iv) the power loss per square meter of surface area.
(OR)
14.b) Take a parallel plate waveguide with ?1, µ1 for Z < 0 and ?2, µ2 for Z > 0 Show
that there is no reflected wave for a TM mode incident from Z < 0 when
15.a)i) What that the attenuation constant due to conductor losses in rectangular wave
guide is provided by
ii) choose with justification the proper wave function for a coaxial wave guide of
inner and outer radii a and b respectively.
(OR)
15.b)i) Show that the instantaneous pointing vector is provided by
S= Re (S+EXHe j2wt)why is S not related to S by usual way.
ii) Suppose a filament of z – directed electric current I i = 10 is impressed along
? ^
the z – axis from z = 0 to z = 1. If E = Uz(1+j), determine the complex power
and the avg. power supplied by this source.
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Earning:   Approval pending.