DS90UB933-Q1: DUT RE EMI Test exceed 4dB @1.6GHz

Hi Amelie,

Can you explain your system a little more? Does the 933 takes in camera data and then it outputs the data to the 934 across a cable? Why did you put the CPU in between the 933 and the 934? is the blue box all one PCB? 

Are you using 10 bit or 12 bit for the 933, 934? is your PCLK for bothe the 933 and 934 31.45 MHz? The FPD-Link data rate is 28* PCLK or 28 * 31.45 MHz = 880.6 Mbps or 440.3 MHz not 1603.95MHz.

Could the CPU be causing the 1603.95 MHz signal?

Regards,

Michael W.

Hi Michael,

yes, this blue box all on one PCB. This is the reprocessing module. The CPU in this board will process the data from camera in advance. After that, transfer to head unit. I have double confirmed with customer and their application is reprocessing data from camera, so both have 933 and 934.

They use 10 bit for 933 and 934. The PCLK is 31.45MHz, which use ti bothe 933 and 934.

I will check with customer whether CPU has impact.

Actually I really confused, is it possible of 51 times harmonic signal of PCLK? Because 31.45MH*51=1603.95MHz? But it is unbelievable! (51 times...)

Hi Michael,

Sorry for bothering you again, just want to confirm again that: is it possible of 51 times harmonic signal of PCLK? Because 31.45MH*51=1603.95MHz? But it is unbelievable?! (51 times...)

Hi Amelie,

Maybe this will help you understand my confusion.

Which of the block diagrams best represents your system?

It is possible that noise at that frequency could be caused by our device but it could also be caused by the CPU. Could you try disabling the 933 or the 934 or both to see which is causing this noise?

Regards,

Michael W.

Hi Michal,

The middle module(933→CPU→934) of the third one is exactly customer's system.

I will ask customer to disable 933 or 934 to have a try.

Thanks!

Hi Michael,

I also discuss with customer whether can disable some module to exclusion.

When they disable the camera module as following, the EMI is OK.

When disable the camera module, actually no data input in 933 but 934 still work.So head Unit will continue to display the last picture.

Any other advice or something can be tried to reduce EMI issue at 1.6GHz?

Hi Amelie,

The issue might be because of the layout of your high speed signals can you send me the layout of the board through email so that I can make sure the layout is ok.

Regards,

Michael W.