Re: [PSES] PoE Injectors

[Scott Douglas]

Thank you to all for the comments on PoE Injectors. Good to know of some 
of the pitfalls when using (re:supplying) these with a product. Not sure 
I want to sign up for the extra workload.


On 10/20/2015 1:09 PM, Richard Jones wrote:
I have also seen emission failures with IP devices using POE 
Injectors, if I remember correctly the emission margin dropped as you 
went up 10MHz, 100MHz to 1GHz. I would think that you would need to 
try a few different types to find a good one and of course unless 
you're working closely with the manufacturer there is no guarantee 
that what you test today will still pass tomorrow :-)

Rich

On Mon, Oct 19, 2015 at 6:06 PM, Doug Smith <d...@emcesd.com 
<mailto:d...@emcesd.com>> wrote:

    Hi Chas and the group,

    It was the design layout of the PCB of the POE, and it was easy to
    see (no PHY used). The magnetics may have played a part but the
    layout is terrible in some of these devices. They are not designed
    by engineers of any competence. In my article, I was very careful
    to make sure the end points of the Ethernet connection and cable
    were not a factor, described in the article.

    There is no PHY in this case, just inductors to inject the DC onto
    the Ethernet connection. No active circuitry was involved as I
    remember.

    Doug

    Department for Continuing Education

    Oxford, Oxfordshire, United Kingdom

    --------------------------------------------------

    Doug Smith

    P.O. Box 60941

    Boulder City, NV 89006-0941

    TEL/FAX: 702-570-6108 <tel:702-570-6108>/570-6013

    Mobile: 408-858-4528 <tel:408-858-4528>

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    --------------------------------------------------




    On Mon, 19 Oct 2015 21:29:14 +0000, "Grasso, Charles"
    <charles.gra...@echostar.com <mailto:charles.gra...@echostar.com>>
    wrote:

        Hello Doug – in your tidbit you indicated that the pwb layout
        was (likely) responsible for the
        increased emissions at the below 100MHz range.  It has been my
        experience that when
        the magnetics are placed inside a connector, that the
        emissions are more influenced from
        the imbalance in the cores and assembly that the layout.
        Nowadays there is literally
        no ambiguity in the layout – the traces go from the phy in the
        SoC to the connector -
        that’s it!  [I am assuming that the design guidelines from the
        connector/phy manufacturer
        are being followed] Also how do you isolate the influence of
        the cable in your measurements?

        After all the internal signal wires could be twisted
        differently as you move the cable... Y/N??

        Best Regards

        Charles Grasso

        Compliance Engineer

        Echostar Communications

        (w) 303-706-5467 <tel:303-706-5467>

        (c) 303-204-2974 <tel:303-204-2974>

        (t) 3032042...@vtext.com <mailto:3032042...@vtext.com>

        (e) charles.gra...@echostar.com
        <mailto:charles.gra...@echostar.com>

        (e2) chasgra...@gmail.com <mailto:chasgra...@gmail.com>

        *From:*Doug Smith [mailto:d...@emcesd.com
        <mailto:d...@emcesd.com>]
        *Sent:* Sunday, October 18, 2015 1:49 PM
        *To:* EMC-PSTC@LISTSERV.IEEE.ORG
        <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
        *Subject:* Re: [PSES] PoE Injectors

        Hi Bill,

        Keep in mind that many POE adapters on the market will cause
        an emissions problem because they are poorly designed and
        unbalance the Ethernet pairs creating common mode currents.

        See my Technical Tidbit at
        http://www.emcesd.com/tt2011/tt080111.htm

        When you open some of them and look at the design, it is
        obvious they were not designed by engineers.

        Doug

        Department for Continuing Education

        Oxford, Oxfordshire, United Kingdom

        --------------------------------------------------

        Doug Smith

        P.O. Box 60941

        Boulder City, NV 89006-0941

        TEL/FAX: 702-570-6108 <tel:702-570-6108>/570-6013

        Mobile: 408-858-4528 <tel:408-858-4528>

        Email: d...@dsmith.org <mailto:d...@dsmith.org>

        Web: http://www.dsmith.org <http://www.dsmith.org>

        --------------------------------------------------




        On Sun, 18 Oct 2015 18:50:30 +0000, Bill Owsley
        <000000f5a03f18eb-dmarc-requ...@ieee.org
        <mailto:000000f5a03f18eb-dmarc-requ...@ieee.org>> wrote:

            Somewhere in the references at the end, you might find
            which devices that these standards apply to.

            There are number of exceptions.  And there may have been
            changes since doc was published.

            In the past I have emailed Victor with questions.

            - Bill



            
------------------------------------------------------------------------

            *From:*Scott Douglas <sdouglas...@gmail.com
            <mailto:sdouglas...@gmail.com>>
            *To:* EMC-PSTC@LISTSERV.IEEE.ORG
            <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
            *Sent:* Sunday, October 18, 2015 2:04 AM
            *Subject:* [PSES] PoE Injectors


            Hello All,

            I am wondering if PoE injectors need to be ErP compliant?
            If so, what
            efficiency level? Does anyone know of any such injectors
            that are compliant?

            The injector would be used to power a product and not a
            switch, router,
            or access point.

            Any and all comments appreciated.

            Regards,
            Scott

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