About Total Gain (Far Field Request)

Altair Forum User

Hi.

I am simulating some antennas and try to make sense about total gain graphs.

In below graph all the antennas close to each other. And i get the following gain pattern for a particular antenna.

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In some angles, gain goes up to 4.0

Then i placed the antennas far away and observed the gain of previous particular antenna.

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I get the maximum gain up to 2.7 only.

We can see that the gain getting closer to its ideal pattern but why the total gain is not much as the gain observed before?

Why it is decreased?

Between these two graphs i only changed to placement of the antennas, nothing more.

Thanks for answers...

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Johan_Huysamen

Hi mustaphos

If I understand correctly you only have a single antenna excited while the rest have no active sources applied.

When the antennas are close together the structures interact strongly and this affects the gain. If the other structures are close by, larger currents will be induced on them and these would re-radiate. In this case it appears that the other structures are acting as reflectors/directors to increase the gain in certain directions. (You should also note that the gain would be decreased in other directions.)

When the structures are further apart, the interaction is reduced and the excited antenna's pattern is then closer to its individual pattern.

Note that, in both cases and assuming no losses, the total radiated power should be the same.

Regards,

Johan H

JIF

Hello mustaphos,

Is this not expected? Consider the extreme case where the antennas are placed infinitely far apart. For that case, the antennas don't influence each other and the antennas can be considered individually. The other extreme is where they are placed extremely close and they will (or could) influence each other greatly and I would expect the radiation pattern to change considerably (increasing or decreasing the gain).

Thus, what you are seeing makes perfect sense to me.