We recently tested our iMX6 DL custom board with DDR3 for EMI and EMC. The board is primarily based on SABRE Platform with PMIC. For layout, we used layer stack-up as defined in SABRE Platform.
We are experiencing an unwanted spike at 230 MHz that exceeds the FCC Class B specified level. We tested up to 6GHz. Everything is fine in complete range except that 220-230 MHz spike. We are unable to identify this frequency either as fundamental or a harmonic for all clock frequencies used in iMX6 and PMIC.
The EMI Lab suggested ferrite beads on all power sources. I was wondering if any member of community has experienced anything like this during their EMI testing and what possible solution is there to this kind of problem.
I'd appreciate your suggestions.
UPDATE: EMI Testing report for our board is attached for reference.