ask for multiband RFID antenna

Hi all..
I'm new in RF, specially in antenna design.
i want to make microstrip RFID antenna with triple band frequency (13,56 MHz, 433 MHz, and 900MHz).
can you give some opinion for me?
how the shape of the antenna?
what technique should i use?

Thx

You can't use microstrip for 13.56 MHz (at least with reasonable dimensions). 13.56 MHz needs an inductive coupler (a coil).

Hali yuda23,
In my opinion you must take a usual spiral coil antenna for 13.56MHz & i.e. in the middle area of the coil (maybe on the other layer of your PCB) you can place an "double band UHF-uStrip" antenna...
K.

For RFID antenna radiation patterns and efficiencies, you can use EM-Core to simulate them.

Infor for download and RFID antenna design can be found at

http://www.pedasoft.com/RFIDPedaSoft.pdf
http://www.pedasoft.com/
http://www.pedasoft.com/PedaSoftEMC.pdf

There are published designs combining 13.56 MHz and 900 MHz, e.g. from aldelaide Univ. in Austrialia. Also I have seen such design in APS 2010 in Toronto. You can just search them for more info. Basically they are realized by placing spirals and dipoles together. Besides, 433 MHz is mostly dedicated for active rfid, which makes it less popular than the HF and UHF counterpart. In addition, I believe there is no such tag chips supporting these three bands together!