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Unformatted text preview: ECE 312 — Autumn Quarter 2010
Exam #2 November 12th, 2010 Write your name below and sign the honor pledge “No aid given, received, or observed” if it
applies. ' There are 3 problems on this exam. Exam is open book and notes.
Please box or underline your ﬁnal answers, and remember to include units.
Be sure to Show all work clearly if you wish to obtain any partial credit. Try to keep your work within the provided space. Use the back of a previous sheet
if necessary. Name: St: iwﬁkeﬁ “The Pledge”: No aid given, received, or observed Problem 1 [3 parts, 40 pointsl
A linearly polarized plane wave propagating in free space has wavelength 5 m and propagates
it + 3“; J2 (a) Write a phasor electric ﬁeld that has these properties (there are many possible answers).
Provide numerical values for the quantities in your expression. (13 points) in direction . The electric ﬁeld amplitude is 0.2 V/m. magnum , tau... awmsﬂwdqrﬂwam E; “or was {3%an m
«~31. .. '(b) Find the time domain magnetic ﬁeld that corresponds to your plane wave. Again provide
numerical values for the quantities in your expression (if not already provided in part (21)). (14 points)
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a" $ﬁ§xéa§ swim, ‘ (c) Find the time averaged Poynting vector associated with your plane wave. Include both
magnitude (a numerical value) and direction. Feel free to use any simpliﬁed equations for this
quantity if applicable.(13 points) TMaA‘ss a. stage dam, mm imeiwiwmwém as; Problem 2 {3 parts: 36 p oints) A 181.6 MHZ plane wave is obliquely incident from amedium having a = 25 so, u = no ,
o = 0 (Region 1) onto aboundary with a medium having 8 = 480, u = no, and c5 = 0 (Region 2). It is known that the eiectrie field in the transmitted region has the form 21' 7‘ 7
E = 5223 14% “)2 (V/rn)
Note the symbols 9i , BB, and 96 refer to the incidence, Brewster, and critical angles respectively. I (a) Is the incident wave perpendicular or parallel polarized or a combination? (7 points) Tim M; ‘ i R I
A ﬁg“; RM vi % &\m§gm “ﬁr that its gagi Nae {M’Q‘Er in leads ram rag Mug" Ex“ "3"; Q ¥te “ring” $ng (b) Which is true? (a) 9i S 90 (b) 9i > BC (0) There is no critical angle in this conﬁguration
(7 points) (c) What ﬁaction of the incident power density is reﬂected? HINT: This problem requires no
computations. (7 points) (d) Find 91.. (15 points) Problem 3 :6 partsz 4 points each}: Circle the best answer. (1) A plane wave is propagating in a lossy medium. What is the skin depth in the medium if the
plane wave power density attenuates 23 H tee of 33 cm? (a) 1.59 cm (b) 6.29 cm “m (d) 21.09 cm (6) none of the above
“a; reﬁghters, mm : w as Sehw‘te“§"§$§“ an alt“ ta“ WW (2) A plane wave is obliquely incident from free space onto a boundary with a medium having
a = 780 , u = no , and (5 i 0 . No reﬂected wave is observed. Which of the following is true? “xg9r¥w74F(W.:ﬁpmw‘&p13,53v)?«gW3Y5Ww1i'xni5ﬁimmﬁﬁmﬁv‘w ﬂpgmw1wnﬁsmmw  Sanam... m www.mwwaarﬁmgwgmuﬁ V v
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(b) the incident ﬁeldmi‘sxpﬂefﬁﬂéiﬁdiiiﬁlafpdlafiied' and the incidence angle is 69.3 degrees a
(c) the incident ﬁeld is parallel polarized and the incidence angle is 20.7 degrees “1:. g9 (d) the incident field is perpendicular polarized and the incidence angle is 20.7 degrees
(6) nOne of the above *jﬁx (3) A plane wave has electric ﬁeld (sz + (j + 1).?)9 (V/In). Thepolarization of this field is:
(a) linear (b) left handed circular (0) right handed circulari (d) elliptigalgl (6) none of the above «WM " (4) A 9.7 GHZ plane wave is normally incident from free space onto a medium having a = 250 ,
n = no, and c; = 0.3 Wﬁacﬁon of the incident power density is reﬂected? y. (a) 0.0294 7&0.0372 (c) 0.0723 (d) 0.0963 (c) none of the above
.... . m; er” 4. .. '
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(5) Under the good conductor approximation, ﬁlt’wh tag ‘5‘ 9 (a) the skin depth is equal to the wavelength
(b) the skin depth increases as the frequency increases
(c) the complex propagation constant is purely real (6) A 4 GHz plane wave propagating in a lossless medium has wavenumber 400 rads/m. The
phase velocity of this plane wave is: (a) 3 X 108 m/s .39 . l ‘ %
(b) 7.50x107 rn/s kt; “g as m m a" “t k} m '9‘ .,. _ id. 7 M: a? p g M .. as was
(0) 6.28 x 10 _ WWWManMAmQ£MM W(d)3 x 107
(e) none of the above ...
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 Johnson,J
 Electromagnet

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