In my circuit, RFID card sometimes works sometimes not. it depends on how I put the card on RFID receiver. Usually it does not work when I put around the smps transformer. I guess SMPS transformer affect RFID card. I cannot change transformer and RFID receiver location. What do you suggest to remove SMPS transformer effect?
If the SMPS really influences the RFID receiver, it is likely to be inductive coupling. This can be tested by removing the RFID receiver from its original place and using a short cable (3-5 inch) to space it away from the SMPS module.
If it is in fact inductive coupling, you can try to shield with ferrite. But I had a similar situation once where I just had to put some copper tape on the SMPS and all worked OK.