basics of rfid tag modulation

Can anyone suggest a link to read more about Tag modulation in UHF rfid?
I want to know how the tag is modulation the carrier wave?

Hello,

entering backstatter modulation RFID into a search engine will give you useful links. If certain questions show up in your mind, you can post them of course.

I need to know Back scatter modualtion is same as ASK or not?
This question is related to EPC Gen2 Protocol.A tag will respond back to reader by back scattering.
As per the protocol two types of modulation a Tag can use, ASK or PSK.In this which equal to back scatter modulation?

Hello,

You can have PSK and ASK at the RF modulation level (backscatter). As the tag changes the load seen by the tag antenna, this may result in both change of phase and amplitude of the backscatter coefficient. Therefore readers should be able to demodulate both PSK and ASK backscatter.

As you may know the standard allows subcarrier modulation. Subcarrier modulation is a form of PSK.Tthe EPC Gen 2 standard is a free download. It is a long document, but it describes how the modulation is done.