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Altera_Forum's avatar
Altera_Forum
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16 years ago

seriallie over coaxial cable

Hi all,

I wonder the SerialliteII can transmit data by a coaxial cable?

how will be the max length?

Thanks....

9 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    To use available high speed IO transceivers with coaxial cables, you would need two cable pairs for each lane. This replacement of a 100 ohm differential pair by two single ended 50 ohm cables is sometimes done for SATA, SAS or PCIe, mainly in a lab for test and measurement. At the lower bandwidth corner of high speed serial links (< 1GBit/s), you can try transformer coupling or active drivers to adapt single ended cables for the link.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Hi FvM,

    Thanks for your replying...

    I found that there are many kinds of coaxial cable ( rg6, rg58 rgxx....),

    I don't know which one to use if I my target bandwith is about 1.5Gbps.

    Could you have some suggestions to me?

    Thanks alot....
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    The questions to ask are:

    1 - What impedance of cable do you need to use (50ohm, 75ohm, etc.)

    2 - What distance (length) do you need to drive.

    As an example, The SDI video protocol at 1.5Gbps can perform at over 200 meters on a 75ohm coaxial cable (Belden 1694). SDI uses a scrambled NRZI encoding. In reality, the length is as much or more dependent on the equalizer at the receiving end as it is on the cable driver at the transmitting end. I expect 8b/10b encoding would perform better with regards to length.

    Jake
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Hi ,

    Can the SerialLite protocal perform over 100 meter over a 50 ohm cable?

    Thanks a lot.

    Kent
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I understand, that requested 1.5 GBPS. It surely doesn't work over 100 m with RG58 or similar "thin wire". You would need a much thicker and more expensive low loss cable.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Belden 7810.

    https://edeskv2.belden.com/products/index.cfm?event=showproductdetail&partid=1820

    Specs show ~8db of attenuation per 100ft. at 3GHz (your 3Gbps data rate with 8b/10b would actually be lower loss than this. So for 100 meters, loss would be about ~26dB. That's pretty good. However, it requires a fairly good cable equalizer at the other end. Stratix IV GX maximum equalization tops out at 16dB. You'll need an external cable equalizer (which would be wise regardless).

    Jake