low frequency band=/ low gain?

[Chest]

Hi all,

I'm designing a mutliband printed dipole antenna now. I faced some problem.
Why the low frequency band is always getting low gain and bandwidth compare with high frequency band? Even getting the VSWR 2:1.

Thanks.

 

[vfone]

Try to reduce the surface waves and radiation in the dielectric material (and increase the gain), putting some via holes around the dipole.

 

[fizi]

you know , larger the physical dimentions related to wavelength more gain for antennas,
as you decrease the fequncy and so increase lambda the gain naturally decreases.
it is the reason .
regards

 

[Chest]

Try to reduce the surface waves and radiation in the dielectric material (and increase the gain), putting some via holes around the dipole.

What do you mean putting some via holes around the dipole? Is it mean like create slot in dieletric material or copper trace?

Do you have any reference for this method? May you upload it?

Thanks in advance.

 

[balaguru thavamani]

Hi,

Gain=efficiency×4piA/λ²

so as frequency increases,λ decreases and Directivity increases which result in

increase in gain.

 

[radiohead]

I think the answer is simple: you in fact scale everything when designing for lower frequencies except the [/b]substrate thickness. This probably makes your design less efficient.