SKR Engineering College 2006 B.E Electronics & Tele-Communication Engineering ELECTROMAGNETIC WAVES AND WAVE GUIDES - Question Paper

VI SEMESTER
B.E. ELECTRONICS AND COMMUNICATION ENGINEERING
EC342 - ELECTROMAGNETIC WAVES AND WAVE GUIDES

Time: Three 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.Define 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.Define 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.Explain why TEM wave is not possible in a hollow waveguide.

9.Obtain 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)Explain 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)Select 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.

Earning:   Approval pending.