Looking for papers about RFID active tag design

I need to design a RFID active tag at 2.4Ghz ISM Band...usage for detects pallets/boxes in Logistics areas. i got te papers frm www.free2move.se
Thy use a Nordic Vlsi nR2401 single chip ( costly) n a PIC 16F87 uP.
I need to redeem the cost ...ny comments frm RFID tag designers, articels r papers needed as my giudance.n i hav sum doubt to be clear out? Thanks in advance