Polarization of antenna

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Alan0354

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I am studying antenna and I have a few question:

1) Is Hertzian dipole linear polarization since the E field is parallel with the orientation of the dipole and radiates out equally out in all Azimuth angle when placed vertically?

2) Same reason as above, a short dipole antenna is linear polarization?

3) Is a horizontally placed loop antenna linearly polarized because E is looping horizontally along the loop and the H is vertical and radiates out equally in all Azimuth angle.

4) What is an example of an antenna that gives rise to a circular or elliptical polarization?

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To Moderator

I think I should have posted this in Antenna section. If you can, please help me move the post to the antenna section as I cannot delete this and re-posting there.

Thanks

Alan
 

The E field component was chosen to be parallel with the dipole element. The H component is therefore orthogonal or normal to it. Take care- in the "far field " only. (1,2,3)

To radiate the circular or elliptical polarization of a wave, the easiest is to use the helical antenna. You can combine two dipoles with a 90-degrees phase shift to radiate the circular polarization.
If you use a waveguide as a radiator, you can generate the circular from linear polarization by inserting a "quarter-wave plate" in it, to generate two linear waves with 90-degree delay, that convert it to circular output.
Best described in Antennas by JDKraus/.
 


if we looking any antenna design and we unknown for which purpose its designed, then how to check its circular or linear or elliptical?

is their any formula to decide the dimension of air box? im using HFSS v11.



Thanking you in Anticipation
 

Chetali said:
if we looking any antenna design and we unknown for which purpose its designed, then how to check its circular or linear or elliptical?
Click to expand...
With experience, you can begin to generally guess the polarization (whether linear or elliptical) by just looking at the design.

In HFSS or other simulation software, you can compare the theta/phi or X/Y components of the radiated fields to measure the linear polarization characteristics. You should also be able to extract information such as RHCP/LHCP/Axial ratio values directly from the software.

If you are truly black boxed, then you can use a linear polarized standard antenna and measure the link strength for different orientations of standard and test antenna. If there is a sharp variation with changing orientation, then the antenna under test is most probably linearly polarized. If there is almost no variation, it is most probably circular/elliptical.

Chetali said:
is their any formula to decide the dimension of air box? im using HFSS v11.
Click to expand...

Distance of lambda/4 (at the lowest frequency of simulation) from the radiating structure.
 

thanks. but by using s/w (hfss) how can i check?
 

I assume that you have a Radiation -> Far Field -> Infinite Sphere already set up.

Right click on it -> compute antenna parameters -> choose the appropriate solution setup -> Press Ok.

You should be able to see the different E-field components, as a quick guide,
a. if Phi and Theta components are vastly different, with almost equal LHCP and RHCP, then it is a linearly polarized antenna. Linear polarization orientation= whichever of {Theta,Phi} is higher.
b. if LHCP and RHCP are vastly different, with almost equal Phi and Theta components, then it is a circularly polarized antenna. Circular polarization sense = whichever of {RHCP,LHCP} is higher.
 
 

jeeudr said:
Go back and read what I said in the previous post.

I gave you instructions on how to generate a report like this :


Also, read this thread: [ https://www.edaboard.com/threads/279596/ ]
Click to expand...




Thanks Jeeudar.

for checking should setup on Last Adaptive ??

im attaching the file 4m which i get the results,from this i can say its circular polarization.View attachment exportparams.txt

actually i want linear polarization, due to slot in center position i get circular polarization.

i have read thread which u refered to me. but i get axial ratio graph is like this , am i doing right design.
but, my polarization is changed, so, can u tell how to see circular Co & Cross polarization
 
hi,
today i get more confused. i was designed on square MSA.when i am using below method at that time phi= theta so i thought its circular, but when i check its axial ratio its above 3 dB that means linear.
so, wt shall i consider this linear or circular ?


thanks
jeeudr said:
Go back and read what I said in the previous post.

I gave you instructions on how to generate a report like this :


Also, read this thread: [ https://www.edaboard.com/threads/279596/ ]
Click to expand...
 

hi,
jeedur,
can u plz explain ur answer i want to check cp of my antenna but i dont understand ur answer ,can u plz specify the figure u attach is showing linear polarization of antenna bkz rElhcp and RERHCP are equal and theta and phi is at 330,350 and 0 degree respectively?then for cp it will be theta and phi same and lhcp and rhcp e.g 80 and 40?????????
 


Do not confuse the E field components along theta and phi with the coordinate systems theta and phi.

For CP, the components Etheta and Ephi should be equal. To check the quality of CP, you can compare the axial ratio (AR). AR < 2 dB is generally good.
 
thanks jeeudr for reply,now if my rEtheta is 6.45 and rEphi is 7 hten can i say my antenna is cp?also minimal value of axial ration in ar v/s frequency curve is 2 db?
 

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