Hi,
>>1.this picture is from the MFRC630 reference manual,Can Crxn and R2 change position?
this is a series circuit, so 2 parts can be changed on positions, but the picture is recommended circuit, suggest you don't change them.
>>Is 3.3V of the radio frequency OK, or must use the 5V radio frequency?
Voltage of TVDD is 3.3V ~ 5V, but if you used 5V, you will get higher field, mean signals quality will be better.
>>3.About the matched res choose,is there any suggestions?
Please refer to schematic of CLRC663 Evaluation board!
Have a nice day!
Best regards,
weidong sun