I did two simulations of the same antenna. I used the same topology(shape) but notDid anyone have the similar experience? Another question, is the dielectric loss a bigger loss than the surface wave loss? I am not sure, although I believe that dielectric loss is not a big deal.
jallem said:I did two simulations of the same antenna. I used the same topology(shape) but notDid anyone have the similar experience? Another question, is the dielectric loss a bigger loss than the surface wave loss? I am not sure, although I believe that dielectric loss is not a big deal.
the same size since the dielectric constant were different and adjusted so both
antennas were exactly tuned to the same frequency.
I used FR4 and Rogers 4350. Rogers gave me an efficiency of 94% while
FR-4 gave an efficiency of 67%, which represented a difference in gain of 1.5 dB.
jallem said:I designed for 2.4GHz. I was using 120 mils but I get the same
results for 60 mils. Only difference is the bandwidth. But, shape
is not relevant in this particular example. Just wanted to point the
difference due to loss tangent. I would guess for 900 MHz the size
you are using must be a "small antenna" and therefore the eficiency
is small. But make sure you got a good matching at the
design frequency.
Added after 5 minutes:
I had experimented with different shapes and some
are better than others but I did not attribute them
to the shape intrinsically but due to the fact that some
shape will radiate more near field than others. In
others words some are more prone to radiate less
near field. It is a conjeture but I dont have the way
to prove it.
jian said:Hi, Bingjian99:
From what my experience, a typical resonance based antenna will store some energy in its proximity. The feed continuous provides energy to the fix with field distribution in the proximity while there is energy radiated out into the space. For a high Q antenna, the energy may not be stored in a very big volume. However, the energy density can be quite high. For a low Q or wide band antenna, the stored energy may not be very big while it needs a bigger space to store it. fix antenna with cut-corners normally are for CP and their resonances are normally very narrow bandwidth. It means that much energy is stored in a very small space and the field intensity is very high here. Any dielectric or metallic loss in the material may cause significant loss of efficiency. I think my comments should explain what is happening in your case.
Best regards,
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