UHF RFID reader antenna for hand held applications

I am developing a reader module antenna 900MHz band (860-930MHz) which should typically have a gain of around 3 dB or so. A microstrip patch is larger and may not be suitable for the application. Prefer to use PIFA and anybody can suggest a better solution, kindly help
If anybody has got an HFSS or CST design example or design file for the PIFA antenna, kindly post it here.

Thannks in advance
Mission

what about the size? you need circular polarization or not?

Circular polarizaton is preferred. We have a space constraint of 10 cm X 5 cm (Length and width). Also need to have a minimum gain of 2-3dBi.
We have found a half disk patch design as explained in the attached paper to explore. Originally the paper talks about smart antenna with multiplehalf disk elements. We want only a single patch element design within our space constraint.
I am also considering to use a high Dk substrate(Use 10.2 material in place of 4.4 FR4) so that the size can be further reduced (8cm -Half circle dimension to closer to 5.5 cm half circle).

1. If anybody can poropose a better method to design an antenna within this space constraint pls. let me know
2. If I design half disk antena how to make it circular polarised?

Any compact and small size (100mm x 50mm x 30 mm) circular polarized PCB antenna design is okay. If anybody has got an idea pls. share.'

Thank you
mission

its possible but it ll not be circular. it ll be elliptical.

Balanis mentions circular polarisation examples with an elliptical shaped patch anntenna (in antenna theory, 3rd edition). It seems to be possible though - with a suitable feed point.

It's possible with elliptical patch but the dimensions will be much larger than than expected.

I didn't check for. What's the radiation pattern of your suggested half-circle patch? Has it linear or elliptical polarization? I fear, it may be impossible to get high performance (gain) and circular polarization with your dimension constraints.

i didnt mean elliptical patch. i mean your polarization ll be elliptical. if it satisfy (Almost all small sized patch(<L/2) have elliptical polarization) your concerns than try it. (my suggestion is i may satisy the demands. i have simulated your half circle patch and with permitivity about 10 it works. but polaization is elliptical (axial ratio changes between 3 to 40 depends on theta. and gain is about 4 dbi, with 30 mm. suspended ground)

Thank you guys for all your suggestions and help. I found a wonderful book byDr.Kin LU Wong on broadband microstrip antennas and hte book has got lots of examples with measured results. I hope I will pick up few and try to simulate and build it.
Thanks again for such a unconditional helping attitude.. Keep it up

if the book is in soft media and has no license problem than post it. i wish to have it too...:)

here is the book