EEL 6509EM Review0
Review of Electrodynamics
EEL 6509 Wireless Communications
Dr. John M. Shea
 Uniform Waves in Free Space
 assume all sources of EM fields are in
same localized region:
 Electromagnetic Fields
 Maxwell's Equations
 In the sourcefree region,
and
,
which implies
 In free space,
and
are related by the permitivitty
:

and
are related by the permeability :
 Complex Vector (Phasor) Notation
 If EM fields are generated at a single frequency, then
each component can be expressed similar to
 Let
(a complex value)
 Then can similarly express E_{y}, E_{z}
 In phasor notation,

 For uniform waves in free space:
 Note that
 This gives us the wave equation for
:
 Simple example

parallel to xaxis E_{y}=E_{z}=0 and
function of z only
 Wave equation implies
 Solution:
 Subsituting solution into wave equation yields:
 Interpretations  on board
 Wavelength and ``speed'' of wave
 Relating Power to Electric Field
 the timeaveraging Poynting's vector is
defined as
 for a uniform wave in free space given by
,
where
is the
intrinsic impedance of free space (
)
 Thus
 The power flux density (expressed in W/m^{2}) is given
by
 In general,
 Thus,
No References!
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John Shea
20010118