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-   -   Question on characterization of elliptical polarization of EM wave. (http://www.physicsforums.com/showthread.php?t=667917)

yungman Jan29-13 06:41 PM

Question on characterization of elliptical polarization of EM wave.
 
I am using "Advanced Engineering Electromagnetics" 2nd edition by Balanis AND "Antenna Theory" 3rd edition also by Balanis. I found an inconsistency in how to characterize RHC (CW) and LHC ( CCW) elliptical polarization.

1) In Advanced EE Page 159, for
[tex]\vec E(0,t)=Re[\hat x (E_R+E_L)e^{j\omega t}+\hat y (E_R-E_L)e^{j(\omega t+\Delta \phi)}][/tex]
[tex]\hbox { Where}\;\Delta\phi=\phi_x-\phi_y≠\frac{n\pi}{2}\;\hbox {where }\;n=0,2,4,6.....[/tex]
If [itex] \Delta \phi ≥ 0 [/itex], then, it is CW if [itex]E_R>E_L[/itex], CCW if [itex] E_R<E_L[/itex]
If [itex] \Delta \phi ≤ 0 [/itex], then, it is CCW if [itex]E_R>E_L[/itex], CW if [itex] E_R<E_L[/itex]


2) In Antenna Theory Page 74,
[tex]\Delta\phi=\phi_y-\phi_x≠^+_-\frac{n\pi}{2}\;\hbox {where }\;n=0,1,2,3.....[/tex]
If [itex] \Delta \phi ≥ 0 [/itex], then, it is CW.
If [itex] \Delta \phi ≤ 0 [/itex], then, it is CCW.

To avoid confusion, just use one example where [itex]\Delta\phi=\frac {\pi}{4}[/itex], you can see using Advanced EE, there are two condition that can give you CW or CCW. But in Antenna, there is only one condition which is CW.

How do you explain the inconsistency? Yes, there are confusion as the definition of [itex]\Delta\phi[/itex] is opposite between the two. But if you look pass the difference, you can still see the inconsistency. Am I missing something?

Thanks

Alan

yungman Jan31-13 10:59 AM

Re: Question on characterization of elliptical polarization of EM wave.
 
Anyone has comment? You don't have to know the answer, just comment on this. This is another inconsistent from Balanis. It is from two books that he wrote.

M Quack Jan31-13 11:12 AM

Re: Question on characterization of elliptical polarization of EM wave.
 
Circular polarization of electromagnetic waves is a mess. There are two different conventions (at least), one predominantly used in visible light optics and the other one predominantly used in radio and long-wavelength electromagnetics.

Basically, you can look at the wave at a fixed time and see how the electric field vector spirals around the direction of propagation, or you can look at a fixed location and see how it spirals as function of time.

Please don't ask me which one is which...

Whenever you publish something on circular/elliptical waves make sure to completely specify which convention you use.

yungman Jan31-13 11:23 AM

Re: Question on characterization of elliptical polarization of EM wave.
 
Yes, from my research, the two main EM book on radio wave that even get into this are Kraus and Balanis. They are using different convention. BUT all the inconsistency are from the SAME author.....Balanis. I know you have to follow one convention.....better yet......one author, but all my question is from the same author!!! That's why it's so frustrating to study this. I have been stuck for like two weeks on this. As you can see, I intentionally bring up all three of my post at the same time to show the questions I have quoting the pages in the books.


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