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CC3200MOD using FCC certification with modified layout

Matt Bennett
Prodigy 170 points
Other Parts Discussed in Thread: CC3100MOD

Hi

I have read the certification guidelines at http://processors.wiki.ti.com/index.php/CC31xx_%26_CC32xx_Radio_Certifications

However, is it possible to change the trace layout between module and antenna and reuse TI's certification? I appreciate I need to use the same (or "similar") chip antenna, but do I actually have to replicate the exact "banana-shaped" fairly long trace used on the evaluation board? This would be rather awkward given I don't use the same PCB design software, but more importantly will significantly restrict my PCB layout options and waste space. Is it not acceptable to follow the antenna layout guidelines in the datasheet, but route it according to my own board? Is TI really expecting everyone's PCB layout to include this long arc trace design?

Ideally I'd use an external antenna. I see the certified design includes a U.FL connector. Can anyone actually make use of it and keep the advantage of TI's certification? I understand no external antennas are listed, but is there any relevance in the line from the webpage:

"If it is desired to add a Murata connector or U.FL connector in the RF path, or change the antenna to one of the same type (chip) with equal or less gain, they can do so without refiling"

Why would anyone add a U.FL connector if they can't connect any antenna to it without needing at least a class 2 change?

Lastly, if customers have to apply to TI for a class 2 change to use an external antenna, has anyone? Would this not be a publicly-available modification (from the FCC site at least) that others could reference? Does TI have any plans to add their own modifications to allow people to use an antenna type other than chip, and/or a layout using minimum space?

Many thanks for any response on this!

  • 0
    TI__Mastermind 27605 points

    Hi Matt,

    I can tell you that the trace length has to be of equal length or longer. This is due to FCC rules, perhaps because if the trace is shortened the radiated power will probably increase, which could cause a lack of compliance.

    If you want to use an external antenna a class 2 permissive change will be needed. This costs roughly half as much as full certification. Because the modular certification grant is under TI's name, there will be some paperwork to be completed.

    Regards,

    Aaron

  • 0 in reply to made4engineering
    Intellectual 500 points

    There is a formula states that 1) antenna length is proportionally to gain (en.wikipedia.org/.../Antenna_gain). So in order to have smaller gain/radiation for compliance, I suspect the length should be shorter?

  • 0 in reply to j_marc
    TI__Mastermind 27605 points
    The Antenna itself should not change. The trace to the antenna can be made longer
  • 0 in reply to made4engineering
    Prodigy 20 points

    There seems to be conflicting information here.

    The wiki states: "In order to take full advantage of the certifications, developers must follow the antenna design/layout guidelines exactly as shown in the datasheet."

    The datasheet shows a different layout than the evaluation board, and it has no dimensions for the trace length.

    There is also a recommendation in the data sheet to keep the RF traces as short as possible, which seems to conflict with the statement given here to keep the traces the same length or longer.

    Then there is the question of the type of antenna.  The wiki states "If it is desired to add a Murata connector or U.FL connector in the RF path, or change the antenna to one of the same type (chip) with equal or less gain, they can do so without refiling."

    the datasheet states, "To use the FCC certification of the Booster pack board, the antenna used should be of the same gain or lesser..."

    There is no reference to using the same type of antenna, only to the gain.'

    And it leaves the question open as to why there is even a connector for an external antenna in the design.  That connector exists both in the datasheet and on the evaluation board.

    Could you please clarify?

    In our application, the board will be inside a metal enclosure so a chip antenna won't work for us.  We will need to use an external antenna.  We need to know whether we can do that and still use TI's certification.

  • 0 in reply to Stephen Gordon
    TI__Mastermind 27605 points
    Hi Stephen,
    The FCC rules are clear when it comes to changing the antenna type: It requires a class 2 permissive change. This change practically will cost about half the cost/effort of doing a full certification.

    -Aaron
  • 0 in reply to made4engineering
    Intellectual 500 points
    Hi Aaron,

    Related to re use of existing FCC and ETSI Certification for CC3100MOD, i have following queries.

    1. The antenna design recommended in datasheet is for 4 layer PCB design.
    2. Antenna signal trace length range is not specified.

    In our design, i am using 8 layer PCB and maintaining the same chip antenna used in reference design as per guidelines recommended by TI except the following.

    1. Antenna trace width is maintained as per recommendation 20mils , but trace to ground clearance is maintained 6mils instead of 18 mils.
    2. Chip antenna (AH316M245001-T) is placed at corner of the Board.
    3. Antenna Trace length is 17.17mm

    With the above deviation still can we use TI's existing certification for FCC and ETSI?
    If we can use the existing Certification? can TI will issue approval certification to use existing FCC and ETSI certificate?

    Also, The CC3100Mod is certified for V1.8.1 which is going to expire by DEC2016.
    Is this Module (CC3100MOD) tested for V1.9.1?

    Please, confirm.

    Regards,
    Harish.
  • 0 in reply to made4engineering
    Prodigy 20 points

    So, to clarify.  Your certificate does not cover any use of the connector with any external antenna?

  • 0 in reply to Stephen Gordon
    TI__Mastermind 27605 points

    Hi Stephen,

    That's correct, the modular certification was granted for a specific antenna type.

    -Aaron

  • 0 in reply to made4engineering
    Intellectual 500 points

    Hi Aaron,

    Any update on my query about Antenna signal routing?

    waiting for your answer to release our PCB for fabrication.

    Regards,

    Harish.

  • 0 in reply to HARISHA BS
    TI__Mastermind 27605 points
    Harisha,

    I cannot verify if your modified design meets FCC requirements. You will have to recalculate and verify yourself

    -Aaron
  • 0 in reply to Stephen Gordon
    Intellectual 780 points

    I wanted to post a quick follow up on this - the Launchpad design files do not match the datasheet recommendations. The Wiki says to follow the Launchpad design exactly and the datasheet recommendations, but they are showing different things. 

    E.g. spacing around antenna trace in Launchpad is 6 mils, but datasheet says to give 18 mils. Can you clarify which should be used and why the discrepancy between the design and datasheet?

    Thank you.