Lect 2.6

# Lect 2.6 - Department of Electrical and Computer...

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Department of Electrical and Computer Engineering ECSE 352 Electromagnetic Waves and Optics 6 Polarization 2.6 Polarization References: Hayt and Buck 12.5 [email protected] 2.6-1 Overview Since the direction of the E-field of an EM wave can point in any direction in space which is orthogonal to the direction of propagation this gives rise to the concept of wave polarization. The simplest type of wave polarization is linear polarization, in which the direction of the electric field vector remains onstant with time However more complex forms of constant with time. However more complex forms of polarization exist, including circular and elliptical polarization. We will see that polarization is a id d h ith f d widespread phenomenon with many forms and applications. ©AGK 2005 ECSE 352 2.6-2 Learning outcomes After taking this class you should be able to: • Describe the concept of wave polarization • List three polarization states and the conditions or them for them • Determine the polarization from a mathematical description of the E or H fields • Determine the instantaneous E or H fields given a description of the polarization state List two circumstances in which wave polarization is important ©AGK 2005 ECSE 352 2.6-3 Contents • Definition of linear polarization • Circular and elliptical polarization • Applications of polarized waves http://webphysics.davidson.edu/physlet_resources/dav_optics/Ex amples/polarization.html ©AGK 2005 ECSE 352 2.6-4

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Polarization • Polarization tells us what the direction of the lectric field is electric field is • This can remain constant with time Linear polarization Or it can change periodically with time Circular or elliptical polarization • Or it can vary randomly Random polarization (natural light) ©AGK 2005 ECSE 352 2.6-5 Antennas FM broadcast antenna ERI Inc. ©AGK 2005 ECSE 352 2.6-6 UHF antenna Indoor UHF/VHF antenna Linear Polarization y E x z Horizontal linear polarization E ©AGK 2005 ECSE 352 2.6-7 Linear Polarization y E x z Horizontal linear polarization E t E t k ©AGK 2005 ECSE 352 2.6-8     0 ,c o s xx x E z tE z  a
Decomposition into x Decomposition into x-and ±y and y- states states E x x yy E z z ©AGK 2005 ECSE 352 2.6-9 Decomposition into x Decomposition into x-and and y- states states E x x E Vertical linear polarization Horizontal linear polarization E E z z    kz t E t z E x x x cos , 0 a  kz t E t z E y y y cos , 0 a

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Lect 2.6 - Department of Electrical and Computer...

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