RFID like design

Hi all,

if anybody could help , I must design a RFID like base station, working @125kHz.
The main difference is that the mobile tag has its own power source, and two antennas, one for reception, the other for emission.
The emitting part is fairly easy, but i am having trouble designing the reception. I'am looking for a low noise opamp, with variable gain, in order to realise a CAG. Any reference used?
The reception machanism is based on A/D sampling, and then signal processing to decode the receive data flow, in order to adapt to fluctuating SNR, and multi mobile receiving.

Any idea of components or achitecture would be great.

Thanks

Narc

You can downlaod some RFID books from EDA E-books Upload/Download Board,
I'm reading now,maybe it can help you !