I don't know about all, but many are. We made a passive tag for
870 MHz with 1kb flash memory and 4 m readout distance last year
(with 0.5W radiated power, now the regulations allow more), but the
ICs are not publicly available.
It's a meaningless question.
There are several RF tag protocols, and lots of special ones.
You actually do need to find out what the RF tag transmits, in
order to be able to specify a reciever.
There may be several protocols, but *the* protocol at 2.45GHz is
probably going to be ISO 18000-4. It would help, though, if Xiangyu
specified what protocol he has in mind, ISO or something else. And
whether it is a passive or active tag. At the time I started the
2.45GHz design I was not able to find complete RFID IC's
and mis-used other short-range radio IC's instead. I know that at
least Philips Semiconductors has been active with the ISO 18000 -
they may have something publicly available by now.
Regards,
Mikko