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Regarding the noise about the AUDM1201

When I add one external CAN communication PCB used IC  AUDM1201 isolation  TX and RX  into the RF receiver moudle,The RF receiver range become shorter. I check it is the IC AUDM1201 problem. I want to  how to aviod the ADUM1201 noise effection . the below sch is Audm1201 isolation.