Is there a relationship between antenna gain and frequency bandwidth?

I can't find a direct relationship or equation between antenna gain and bandwidth in the literature. Is there a relationship?

In my simulations, I do observe that as bandwidth of antenna increases, gain in general decreases.

Could someone explain the relationship between the two physically?

Thanks.

When bandwidth increased, then antenna (or part of it) can not resonate at full power at some frequency. I think relationship is something near formulas about oscillation modes and wavelengths.

In general, there is no direct relationship.
Although, for some particular type of antenna and bandwidth-enhancement technique, it can be true.
Regards

Z

The gain is frequency depend, so you can get from the same antenna more gain at a higher frequency than at a lower.
This could lead to different gains at different frequency points, and perhaps decreases the antenna gain from an antenna with a very large bandwidth.

By the way, what gain is stated from an antenna with large bandwidth? The lowest?

I believe you are wrong. There is a theoretical limiting relating the Q (which is related to bandwidth), gain, and the volume of a sphere enclosing an antenna

http://www.giangrandi.ch/electronics/anttool/gain.html

That said, I think there is no practical way to get near this maximum theorectical value.

Dave

That page seems to list a few very interesting articles.

Though, it does seem to make some restrictions: linear polarized, omni-directional ?

Hi Dave,

It't true that there exists such a limitation between antenna size and bandwidth. But what I said is that In general, there is no direct relationship between antenna gain and bandwidth. I.e., there is no a general rule that can be applied to all cases.
Regards

Z