Hello Junjie,
See following, please!
(1) SL3S4011 supports ISO 18000-6C protocol .
(2) Antenna.
SL3S4021 IC supports double antenna, but due to the complexity of UHF working environment, it is very hard to give a standard desgin for double antenna in our application note, if your project has been carried out, you can contact our NFC Read + SMR (TAG&LABEL) team through NXP marketing or sales, they will provide many valuable suggestions to you!
Best Regards,
Weidong