[SI-LIST] Re: HDMI Frequency Failing RE Test by 7dB!!!!
- From: Ken Wyatt <ken@xxxxxxxxxxxxxxxx>
- To: ah.vinod@xxxxxxxxx
- Date: Wed, 23 May 2012 09:26:16 -0600
Vinod,
Is the HDMI connector shield -directly- connected to the (metallic) enclosure?
This should ideally be multiple connections. If the shield is floating or
poorly connected, you'll get common-mode currents flowing along the outside of
the HDMI cable shield.
Have you measured the common-mode currents with a current probe?
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On May 23, 2012, at 9:17 AM, vinod ah wrote:
> Hi Vijay,
>
> We have option to control the current and voltage swing. We tried
> both, without violating eye test, but still the i am seeing radiation
> at 742.5MHz. The radiation level keeps chnaging as i try with multiple
> cables. I found the best cable i had to be failing FCC limits by 7dB.
> I used some HDMI cable which are sold by big brands, but i was failing
> FCC by 12dB !!!.
>
> Hi Boris,
>
> We tested the Blu ray player and TV with same HDMI cable used for our
> board testing. the Blu ray player used is from Sony while the TV is
> from LG, we connected the blu ray player to TV using same HDMI cable
> and took the readings.
>
> Regards
> Vinod A H
>
> On Wed, May 23, 2012 at 8:43 PM, Traa, Boris <boris.traa@xxxxxxxxxxx> wrote:
>> Dear Venod,
>>
>> You said that TV is oke and Blu Ray is tested. Seperately or as a
>> combination with the same cables you also used to attach your board?
>>
>> Kind regards
>> Boris Traa
>> System design engineer EMC
>>
>> It's the currents that make circuits work or fail.
>>
>> Philips Innovation Services/EMC center
>> Room 2.020
>> High Tech Campus 26
>> 5656AE Eindhoven, The Netherlands
>> Tel: ++ 31 40 27 43766
>> Fax: ++ 31 40 27 42224
>> E-mail: boris.traa@xxxxxxxxxxx
>>
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>> Behalf Of vinod ah
>> Sent: Wednesday 23 May 2012 3:58 PM
>> To: SI-LIST
>> Subject: [SI-LIST] HDMI Frequency Failing RE Test by 7dB!!!!
>>
>> Hi All,
>>
>> I am designing a board with HDMI input and HDMI output. I am facing EMI
>> issue at 742.5MHz (failing FCC limits by 7dB) when running 1080p30 on both
>> Input and output HDMI i.e. BLu ray player connected to HDMI input connector
>> of my board is giving out data at 1080p30 and HDMI out of my board is
>> connected to TV which is also 1080p30 content. So i am unable to find out
>> how is 742.5MHz coming out as radiation as it is 10th Harmonic of pixel
>> clock 74.25MHz!!!!!!!. I am not facing any issues with other harmonics
>> except for this. So i am totally confused on how to go about debugging this
>> issue.
>>
>> Note: All the signals are routed on top layer without vias and all signals
>> have solid ground plane reference. The blu ray player and TV used, is tested
>> for radiation and no significant levels seen.
>>
>> Regards
>> Vinod A H
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