Axial ratio & frequency by CST

[tazari]

Hi everyone ,
I have a question about the CST MWS. how plot the axial ratio of the antenna vs frequency?
for exempl

Thanks.

 

[jeeudr]

Make sure that you have Field Monitors for all the frequency points that you are interested in.

Use the Template based Post Processing (Shift-H) option to generate the plot. In that go under 'Farfield and Antenna properties' -> 'Farfield Result'. Set the monitors and direction as you want. The frequency option should be set to 'Broadband' and the value to be plotted to 'Axial Ratio'

 

[tazari]

Hi jeeudr. Thank you for your reply.
i don't have similar courb, can u see my procedur in pictur and result ?
Thank you!

 

[9009484]

Hi tazari and jeeudr
this question is my question also.
jeeudr, I have done these steps but finally I gained Directivity versus frequency, I want axial ratio versus frequency, may you help more?

 

[jeeudr]

Both of you are very close to the final step.

In this picture, look at the top right drop-down menu in Farfield Settings. In the Plot Mode drop-down, change from Directivity to Axial Ratio. Also, click on the Axis/Polarization button and change the Polarization to Spherical.

View attachment 98253

 

[9009484]

Dear jeeudr
it's true, but In the Plot Mode drop-down, I can't change from Directivity to Axial Ratio because there is'nt axial ratio option for selecting

 

[jeeudr]

Sorry. My mistake.

1. Change the Plot Mode drop-down value to either Gain or Realized Gain.
2. Click on the Axis/Polarization button and in the pop-up window set Polarization to Circular.
3. Set the Axis/Polarization drop-down value to Axial Ratio.

 

[9009484]

sorry, at this time i can't plot axial ratio, the result is gain versus frequency. what can I do?

 

[jeeudr]

Change the value in the drop-down box (blue highlight in the picture) to Axial Ratio.

 

[9009484]

this is the result that i have received from your setting
**broken link removed**

 

[tazari]

Re: Axial ratio & frequency by CST

For me to i have this result !

- - - Updated - - -

but othr step i have this result

 

[jeeudr]

Re: Axial ratio & frequency by CST

For me to i have this result !View attachment 98267

- - - Updated - - -

but othr step i have this resultView attachment 98268View attachment 98269

1. Do not worry about the title of your plot, you can change it in the Post-processing templates window. For now, it just retains your old title of Directivity. If you want you can delete that and start over.

2. You have set your theta value to 90 deg. The Z-axis is theta = 0 deg. So if your antenna is in X-Y plane and boresight direction is along Z-axis, then you might want to set theta to 0.

- - - Updated - - -

this is the result that i have received from your setting
**broken link removed**

I cannot see the picture that you have linked.

Either use this forum's default uploading option or imgur.com to upload your image.

 

[tazari]

Re: Axial ratio & frequency by CST

Tank u very mutch jeeudr , so for thta =0 i have this results but i don't have AR<3 i don't have cirulare antenna !

- - - Updated - - -

Tank u very mutch jeeudr , so for thta =0 i have this results but i don't have AR<3 i don't have cirulare antenna !

 

[jeeudr]

Re: Axial ratio &amp; frequency by CST

Tank u very mutch jeeudr , so for thta =0 i have this results but i don't have AR<3 i don't have cirulare antenna !View attachment 98271View attachment 98272

The results indicate that your antenna does not have circularly polarized radiation.

 

[tazari]

Re: Axial ratio &amp; frequency by CST

Thank u jeeudr for ur help

 

[tazari]

Re: Axial ratio &amp; frequency by CST

Dear jeeudr
We can say that this antenna is circular on the 900 MHz band?
Thank u

 

[jeeudr]

There is no fixed point where an antenna stops being linearly polarized and then starts being circularly polarized. It is a spectrum of values, and the closer your axial ratio is to 0 dB, the better your circular polarization.

Some systems have a requirement of AR < 3 dB, while some others need AR < 2 dB.

So depending on your system specifications, the performance you show might or might-not be enough for the 900 MHz band.