Dear All,
A customer is facing dome issue in emission on a custom board.
During Radiation Emission testing of a product based on DM8168, I found below frequency radiations from the board.
1) 444~445MHz: With the help of near field probe, I figured out that this frequency is being radiated from the traces of HDMI which is TMDS direct interface of the processor with HDMI connector. This is probably 3rd harmonic of 148MHz frequency on which this 1920*1080p resolution works. We have followed complete guidelines mentioned in the processor from Schematic and Layout point of view. Is there any way to reduce this radiation through software? I mean is there any slew rate control register or any other control to reduce the radiation?
2) 398~399MHz: With the help of near field probe, I figured out that this peak frequency is being radiated from the traces of DDR3 interface. More, I also found complete frequency band (350-650MHz) being radiated from this area. I am using the same DDR3 interface and DDR3 parts as EVM based on DM8168 made by Spectrum Digital. I also found the same kind of radiation in the EVM board mentioned also. We have followed complete guidelines mentioned in the processor from Schematic and Layout point of view. Is there any way to reduce this radiation through software? I mean is there any slew rate control register or any other control to reduce the radiation?
Could you please help?
Best Regards
Feroz
