co-polarization and cross-polalization pattern

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sanders

Joined: 21 May 2006
Posts: 129

26 Jun 2006 13:09 co-polarization

how to get the co-polarization and cross-polalization pattern after post procession using HFSS?

Best regards!

heedavid

Joined: 21 Apr 2005
Posts: 58
Helped: 4

28 Jun 2006 3:40 co polarization

Dear sanders,

One good way to remember 'identifying' such things as co- and cross-pols is to remember:

E-co is always parallel (i.e. in the same direction) to the current flow on your radiator. E-cross is naturally orthogonal to it.

H-co is simply orthogonal to the E-co, and again, H-cross is orthogonal to its H-co.

Hope this helps,
Dave

azremi

Joined: 11 Jul 2006
Posts: 23
Helped: 2

13 Jul 2006 4:09 co and cross polarization

Still not clear Very Happy

Do you have an image explaination to clear this doubt? Thanks!

helio1972

Joined: 30 Oct 2003
Posts: 93
Helped: 5

14 Jul 2006 1:03 co-polarization and cross-polarization

You need to define the sphere with theta and Phi, or obly a 2D with phi of
two values 0 and 90 degrees.
At Phi=0---> E filed is in Theta direction, theta gain=copol gain and phi
gain=cross pol
At Phi=90---> the E filed is in the phi direction. The copol is phi gain and
teh cross-pol is the theta gain.

Boomerang

Joined: 23 May 2006
Posts: 13
Helped: 1
Location: USA

14 Jul 2006 1:12 copolarization

Hi helio1972,

I find this topic interesting. I'm not very knowlegeable of antennas. So, for a given antenna, is it desired to have Phi=0 pattern equal to Phi=90 ?

azremi

Joined: 11 Jul 2006
Posts: 23
Helped: 2

14 Jul 2006 2:11 circular polarization cross pol

Thanks Helio,

It helps a lot. But, how about the co and cross polarization for H field? transverse to E field?

I've seen lots of journals and proceedings for antenna radiation, but most of them with different understanding or probably different way of presentation. So what normally people expect, or intend to know from radiation pattern?

Thanks again Wink

azremi

Joined: 11 Jul 2006
Posts: 23
Helped: 2

25 Jul 2006 10:16 co-polarized

Still not clear...anybody can explain on this?

jallem

Joined: 23 Jul 2005
Posts: 477
Helped: 67

25 Jul 2006 15:32 co polarization cross polarization

co-polarization means you meaure the antenna with
another antenna oriented in the same polarization
than the AUT. Cross-polarization means that you
measure the antenna with an antenna oriented 90
degree with respect of the main polarization.
In others words cross-polarization is a measure of
how much linear the antenna is.
When the antenna is not linear for example as in
circular polarized antennas, then cross-polarization
is a measure of how "circular" polarized the
antenna is.

azremi

Joined: 11 Jul 2006
Posts: 23
Helped: 2

27 Jul 2006 9:18 what is co polarization

how can we know the polarization of an antenna?

Is the polarization for all microstrip patches are the same?

So, the cross-pol can be done by rotating 90 degree of the transmitting or the receiving antenna?

Thanks all!

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27 Jul 2006 9:18 Ads

eirp

Joined: 11 Dec 2001
Posts: 639
Helped: 9
Location: Phase center

10 Aug 2006 15:38 co polarized antenna

azremi wrote:

Polarization of antenna is given by E field distribution or electric currents (they produce E field in the same direction as the surface current dir.).
Visualizing currents on ms patches is thus usefull for checking the radiated polarization.

For co and cross fields, Ludwig3 coordinate system is very usefull. I quote few words from CST MWS manual:

Ludwig 3: The theta and phi components of the farfield can be transformed to the "Ludwig 3" representation. Please note that this transformation is usually done with the main lobe aligned to the z'-axis (see Farfield Plot - Axes and Vertical and horizontal polarization). Therefore the phi and theta angles below refer to the main lobe aligned coordinate system. The vertical and horizontal component are calculated as follows:

$3$E_{horizontal}=E_{\theta}cos(\phi)-E_{\phi}sin(\phi)\\E_{vertical}=E_{\theta}sin(\phi)+E_{\phi}cos(\phi)$

Note: Co and Cross Polarization are identical to the Ludwig3 representation. Depending on the direction of the electric field the excitation mode, vertical and horizontal have to be linked with cross and co polarization. The vertical component always directs in y-direction (y'). Therefore in the case of Ey as the main waveguide mode component, the Co polarization is identical to Evertical and Cross polarization is identical to Ehorizontal.

Best!

eirp

costox

Joined: 05 Mar 2002
Posts: 209

13 Aug 2006 0:22 what is co-polarization

Dear EIRP,
From experience, what do you use for an array of planar dipoles:
Ludwig 2 (azim over elev), Ludwig 2 (elev over azim), or 3?
To be honest, I have no clue which plot to select since they all have different beamwidth.
PS: by the way, do you find it annoying that with MWS, you cannot select all the point using the mouse ? (I mean you have to double-click 50 times if you want to pick 50 points on your antenna).

eirp

Joined: 11 Dec 2001
Posts: 639
Helped: 9
Location: Phase center

13 Aug 2006 22:06 what does cross pol mean?

costox wrote:

Dear Costox,

Arrays arent my main interest but for most of my design Im happy with spherical and ludwig3. How the BW differs in your design?

Please could you describe in details what you mean in picking. I guess to select all "pickable" points in one click? What reason for that?

Cheers

eirp

costox

Joined: 05 Mar 2002
Posts: 209

13 Aug 2006 22:29 co-polarization

Eirp,

I'm a beginner w/ MWS, I'm still trying all the combinations ludwig2-3 with different theta/phi/alpha/epsilon angles to get the best view...

Regarding the selecting points:
for example, I want to select all the points of the upper surface of a printed dipole array, so that I can extrude it (to increase the thickness of the traces), but I could not slide the mouse over all of the clickable points and select them all IN ONE SHOT... I've tried everything... But the only way right now for me is to double-click the point one-by-one, very annoying because my array is big and there maybe 20-100 points to select.

Maybe because I have MWS5.

Another annoyances: 1) when you sweep, you have to sweep a close curve, not an open curve. I tried open curve and it didn't work. 2) when you sweep, you have to select 2 curves, the model and the path. In HFSS, you just click on the model, then type in the distance and the direction you want to sweep, therefore it's faster in HFSS.

cuongtran

Joined: 06 Feb 2007
Posts: 183
Helped: 4
Location: WhiteHouse

28 Jun 2009 15:08 cross polarization and co-polarization

To costox
- To extrude, why dont you choose ALL THE Surface (there is a button, red rectagular if i dont hav mistake), you click on this button then your surface,
- Sweep ....: dont know what u said.