The major factor of efficieny of tri-band PIFA?

Hi all,

I am simulating tri-band planar antenna in which S11 of all resonant frequency is only around -3.5dB, I would like to have some advice on what major factor to affect antenna efficiency.

Best Regards,
Le :o

The reason may be impedance mismatch.

In this document you can find the formulas that can tell you how much efficiency are you losing due to mismatch loss.
http://www.tdkrfsolutions.com/DataPD...aper_part1.pdf

check this

Ok, it seems to be good.
Thank you

Very nice for TDK RF antenna_paper