How to demodulate UHF RFID Tag and Reader signal...

I have to know UHF RFID Tag and Reader communication signal.
I can use cable to connect tag and reader.
Whether there is demodulation circuit that can offer reference.
thx~

You'll have to give us a little more information

1)
First are you trying to demodulate the reader to tag signal or the tag to reader signal

2)
Is this an EPC Protocol tag? (Gen1 or Gen2)?

3)
How are you connecting the tag to the reader?
If you are using a commercial tag there are only two ports for the antenna. No direct data lines.

I do a lot of research in RFID and related fields so i may be able to answer your question quickly if you give a little more info.

Cheers