em wave propagation and polarisation

8/13/2019 EM Wave Propagation and Polarisation

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EM wave propagation and polarization in

different media


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Outline

Introduction Electromagnetic Wave Propagation Polarization Linear

Elliptical Left Handed Right Handed

Circular Left Handed Right Handed

Summary Demonstration of Matlab program References


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Introduction

A Matlab based GUI/Apps are developed in Matlab 2013a to

studies the polarization of an electromagnetic wave propagating

in different media like 'Free Space' or 'Lossy Media'. A Graphical

User Interface is used for the demonstration of the behaviour of

EM wave propagation under different media and different EM

wave polarization. Programmatically, the sense of rotation in EM

wave with circular and elliptical polarization is demonstrated

using animated fields.


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ELECTROMAGNETIC WAVE PROPAGATION

Electromagnetic wave composed of two component : Electric field

and Magnetic field. The relations and variations of the electric

and magnetic fields, charges, and currents associated with

electromagnetic waves are governed by Maxwell's equations.

t

EJJH

t

HME

qH

qE

ci

i

mv

ev

(1)

(2)

(3)

(4)


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WhereE = Electric field intensity

H = Magnetic field intensity

Ji = Impressed (source) electric current density

Jc = Conduction electric current densityMi = Impressed (source) magnetic current density

qev = Electric charge density

qmv = Magnetic charge density

When we talk about propagation of EM wave, we consider thatwe are far from source region.

So far a source free region

Ji , Mi ,qev and qmv = 0

ELECTROMAGNETIC WAVE PROPAGATION contd.


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rk

rk

tj

o

tj

o

eHH

eEE

In an unbounded medium EM wave travel in TEM mode. If we consider a

wave traveling in z direction having E-field in x-direction and H-field in

y-direction. For a lossy medium equation (5) and (6) turn into the form as

z

z

z

z

tjz

oy

tjz

ox

eeHH

eeEE

(5)

(6)

(7)

(8)

On solving Maxwells equations for time harmonic varying fields, E and Hcome in the form of

0

ELECTROMAGNETIC WAVE PROPAGATION contd.

(for free space )


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According to the IEEE Standard Definitions for Antennas, the

polarization of a radiated wave is defined as that property of a

radiated electromagnetic wave describing the time-varying

direction and relative magnitude of the electric field vector.

Polarization may be classified into three categories: linear, circular

and elliptical.

If the electric field vector at a point in space as a function of timeis always directed along a line, which is normal to the direction of

propagation, the field is said to be linearly polarized.

POLARIZATION


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If the electric field vector trace is an ellipse, field is said to be

elliptically polarized.

If the electric field vector trace is a circle, field is said to be

elliptically polarized.

Linear and circular polarizations are special cases of elliptical,

and they can be obtained when the ellipse becomes a straight

line or a circle, respectively.

On the basis of sense of rotation of electric field vector, wave is

called as right-hand polarization or left-hand polarization.

POLARIZATION contd.


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POLARIZATION contd.


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POLARIZATION contd.


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POLARIZATION contd.


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POLARIZATION (Summary)


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References

C. A. Balanis, Advanced EngineeringElectromagnetic, 2 Edition, Wiley Publication.

Matlab 2013 Documentation.

em wave propagation and polarisation

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