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zhiweisim
Joined: 19 Feb 2009
Posts: 25
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 19 Apr 2009 22:55 co polar and cross polar in cst |
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Hi,
Can anyone please tell me how to determine the co and cross polarization of E and H plane for a patch antenna in CST MWS?
I have designed a circular shape microstrip patch antenna lying on x-y plane and the electric field is flowing along x-axis (as viewed from the E-field monitor)
Also, may I know how to perform the measurements of co and cross polarization of this rectangular patch antenna in the lab?
Please help. Thanks.
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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20 Apr 2009 7:42 why 45° cross polarized wikipedia |
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Hi,
try my attachment there:
http://www.edaboard.com/viewtopic.php?p=1139416#1139416
page 18
Is it OK ?
Added after 16 minutes:
| zhiweisim wrote: |
Hi,
Also, may I know how to perform the measurements of co and cross polarization of this rectangular patch antenna in the lab?
Please help. Thanks. |
So, you need Friis formula,
http://en.wikipedia.org/wiki/Friis_transmission_equation
(Basic form of Friis Transmission Equation)
may be try http://wireless.ictp.it/handbook/C6.pdf
so you need
1) 2 the absolutly the same antenna and use Friis formula
or
2) 1 know antenna and your antenna and use Friis formula (you have 2 equation/ 2
or
3) 3 unknowns antenna ((you have 3 equation/ 3 unknows gain)
if you measure cross, you must turn one antenna on 90°.
I hope, that you understand me and I helped you, if no, give me question...
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zhiweisim
Joined: 19 Feb 2009
Posts: 25
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20 Apr 2009 9:34 cross-polarization of antenna, vector |
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hi mauloftin,
I have looked at the attachment from your previous post. But, I still not quite understand. From the attachment, it stated that 'the co polarized farfield component has the same polarization as the excitation'. May i know what is the 'polarization vector (y' axis) - X, Y, Z' for my case? Attached is my antenna structure with a probe feed below the patch.
Also, when performing the lab measurements, when I placed the circular patch antenna vertically on the rotational turntable, where this patch structure directly facing the standard gain horn antenna, am I measuring its E plane or H plane? if I am measuring the E-plane, then how should I place the antenna to measure its H plane?
Please help.
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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20 Apr 2009 11:28 ludwig 3 polarization |
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Hi,
so - polarization vector - in the set of port is "polarization angle", it is , where is the vector E - try set different angles and look at the port, how to change the vector E (may you must set "Text size" as large) - attachment
so the polarization vektor is, where is vector E, in your case is X 0 Y 1 Z 0. Understand me ?
measuring: If you measure in H plane, you must turn on 90° BOTH antenna (your patch and horn) , it is easy 
Is it OK ? Give me question, if you do not understand me.
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zhiweisim
Joined: 19 Feb 2009
Posts: 25
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20 Apr 2009 12:29 cross polar ludwig 3 wiki |
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hi mauloftin,
Sorry, I cant get you for the first part. Why we have to set the polarization angle as 90 degree in my case? I can see two arrows from the 'Port' section, one is the red arrow pointing at z-axis and another is the green arrow pointing at y axis. What does they mean?
Can you explain in more details. Thanks.
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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20 Apr 2009 12:59 measuring cross polarization |
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How do you want to have, you can set pol.angle. But usually is 90° - in to axes Y. You can set for example 45°, but you must set polarization vector X 1 Y 1 Z 0. If you do not set pol.angle, he set itself, if your port rectangle, the vector will be parallel to the shorter side. The red arrow is only direction where port radiates. Green is vecotr E.
But may be: I do not know exactly, what your antenna is polarization. Exactly: why is your source eccentric ? Exactly, if you are measure antenna, where is your port, is it down or the right, left or up ?
eeee sorry, it is my mistake. Your patch antenna have source and it is coax, so polarization angle of port - it does not matter. You must only set pol.vector X 0 Y1 Z0, because this is polarization of your patch antenna. You can see in coordinate system Ludwig 3. If you set pol.vec. X 0 Y 1 Z 0, you see, that copolar radiation pattern is good, normal, but cross is bad. I hope, that you understand me....
Last edited by mauloftin on 20 Apr 2009 13:43; edited 1 time in total |
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zhiweisim
Joined: 19 Feb 2009
Posts: 25
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20 Apr 2009 13:42 copolar field wikipedia |
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| Can you attach the co and cross poalrization plot that you get? Also, in my case, how do I know whether my antenna is vertically or horizontally polarized? Please advise. Thanks.
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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20 Apr 2009 14:27 what is circulare cross pol |
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| zhiweisim wrote: |
| Can you attach the co and cross poalrization plot that you get? Also, in my case, how do I know whether my antenna is vertically or horizontally polarized? Please advise. Thanks. |
Uf,it is not easy to explain . And my native language is not English (you can see it  )
So:
copolar: You must set polarization vektor, for example X0 Y1 Z0 and look at farfield for example for Ludwig 3 Horizontal - you see, that farfield is "normal", typical similar to dipole antenna. It is your copolar. the vector E is in X axes, because is it Horizontal.
If you can measure copolar, you must get your connector down and your measuring horn have longer side down. You can measure E plane cut of farfield. You can turn on 90° both antenna and you can measure H plane cut farfield.
cross polar: Is the same: Ludwig 3 Vertical - you see, that the farfield is not so good, is it cross polar.
If you can measure copolar, you must get your connector right (or left, is it the same case) and your measuring horn have longer side down. You can measure cross E plane cut of farfield. And can turn on 90° both antenna and you can measure cross H plane cut farfield.
Uf, I hope that you understand me So give me question , But I must go home now, so see you later (tomorrow) Good Luck
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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21 Apr 2009 6:50 cross polar gain wiki |
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Good morning
So what your project ?
I was thinking about it. It is stupid system I think, that there is problem only with coordinate system..... I hope, that I helped you a bit. I think, that I am right, but I am not sure..... try use help in CST .....
Have a nice day
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zhiweisim
Joined: 19 Feb 2009
Posts: 25
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28 Apr 2009 10:40 gain equation of a circular patch antenna |
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hi mauloftin,
I still cannot understand. So, for my antenna, the co-polar direction is x-axis and cross polar direction is y-axis? Also, what does it mean when I set the polarization vector as 'X0 Y1 Z0'?
Can you explain it in your native language (Mandarin) as I understand Mandarin as well. This is my email address : jetlithebest(at)hotmail.com. Thanks for your help.
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mauloftin
Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ
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28 Apr 2009 11:35 circular patch antenna e and h plane description |
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Hi,
it is long time
so, sorry, but my question is: do you know , what is "polarization" exactly ? What does it mean ?
It is about electromagnetic wave.
http://physicslearning.colorado.edu/PiraHome/ResourceCD/ResourceImages/PhysicsDrawings/EandM_Wave.gif
You have E ( Electric vector)
and perpendicular to the E is H (magnetic vector)
and if you draw this "elektromagnetic wave" to the cartesiancoordinates, the polarization vector say only, where is your E - which axes is
parallel to the E.
And antenna have polarization. It is say, what is orientation your antenna. In the horn antenna (waveguide) - for example - the E is perpendicular to the longer side. If you have (for example) 2 horn
and set is to the same orientation, you can measure good transmission. If you turn on 90° first horn, you can meassure bad transmission.
And it is the same in CST. I dont know what does mean Ludwig 3 "Horizontal" and "vertical" (try help) exactly, but you see, that first set: is bad transmission (gain) - you see cross polar, and second set: you see good gain -it is your copolar.
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