Input Impedance for 2.4GHz (ISM) band RFID Tag Chip

I'm about to design an RFID tag antenna which operates at the 2.45GHz band. To acheive conjugate match，the impedace of the Tag Chip must be known. I have searched for several days, but didn't find. Did anyone have experience on this kind of tag chip?

I decide to change the RFID tag chip. Monza4 of Impinj which operates at UHF band is selected. Now, the design of tag antenna is in process.