Comparison of two antenna polar plots

[huytergan]

Hey there,
I added two plots belongs to two antennas. The one which at 5.69 GHz has gain of 1.7 dBi whereas the other one at 7.08 GHz 3.7 dBi.

Aside from that gain comparison, is it possible to say 5.69 GHz antenna better in those comparison regarding the plots?

Note that two antenna sizes are same.





Be Safe,
Regards.

 

[gyz182]

Firstly, better for what? Secondly, you might like to confirm, but it appears that your gain values are actually negative.

 

[huytergan]

when I look at 3D farfield plots, gains like I mentioned above. Shouldn't I look at there? I don't understand why they're different. It shoulda been same.

 

[gyz182]

What would you like to use the antenna for? Are you after large bandwidth? Omnidirectional or not? By looking at the antenna farfield plot, you will gain an idea of the radiation pattern (ie. Which direction do you get maximum radiation?)

It should be different. As you've mentioned the antenna size are the same. The size of an antenna is related to the frequency/wavelength. Therefore, I will not expect an antenna of the same size (assuming they're the same type) to behave the same. The gain will increase as the frequency increases.

 

[huytergan]

You got me wrong. You said my gain appears actually negative. (regarding to main lobe magnitude) But, at 3D farfield plots, they're positive. Why those are different that's what I didn't understand. I'm talking on microstrip patch antenna btw. When size being smaller, frequency increases and gain decreases.

 

[volker@muehlhaus]

You said my gain appears actually negative. (regarding to main lobe magnitude) But, at 3D farfield plots, they're positive. Why those are different that's what I didn't understand.

Perhaps one is gain (reference is input power) and the other is directivity (reference is total radiated power). Directivity ignores the losses in the antenna and just looks at the radiated power.

 

[huytergan]

Perhaps one is gain (reference is input power) and the other is directivity (reference is total radiated power). Directivity ignores the losses in the antenna and just looks at the radiated power.

Nope, both are gains. I changed the 'cut angle' to 0. It became omnidirectional and gains are almost same with 3D farfield plot. mind if I ask what 'cut angle' should be for simulations?

 

[vfone]

Looking to the pattern plots, I think none of your antennas resonate to the frequencies where you are checking the gain.
What is the return loss (or VSWR) of the antennas at 5.69 GHz and 7.08 GHz?

 

[volker@muehlhaus]

mind if I ask what 'cut angle' should be for simulations?

Whatever is relevant for the application.

It seems that you start from an arbitrary result (call it solution) and now try to find a problem to fit your solution ... :roll: