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CC3120MOD: CC3120MOD and Ground Plate

Benjamin Couture
Prodigy 140 points

Part Number: CC3120MOD

Hi,

We recently had a big change in the design for our controller. Now we are adding a bottom metal plate (aluminum 1mm). Like my little drawing shows, the metal plate support will come pretty close to the antenna from the bottom. This system is attached to the frame of a truck, so there is no communication expected from the bottom anyway. But I was wondering how much of the emission in the other directions will be affected. Would it cause components to overheat, will it cut most of the emission upward? I'm not very much familiar with radio emission.

The antenna used is the same as the one from TI evaluation boards; AH316M245001-T

Also I don't know what would be the best, having the bottom plate grounded or floating?






  • 0
    TI__Genius 13710 points
    Hi Benjamin,

    With the metal being directly under the antenna this will definitely effect the antenna performance. There should be no concern with overheating of the antenna. What you can do in the lab would be the following:

    1) With no metal below look back into the antenna with the current matching network and see what the S-parameters look like (this would be S11 and would be your baseline). I would expect for a good match that you see a RL < -15dBm or so in the 2.4-2.5GHZ band.
    2) Next add the metal below the antenna with it floating and then with Ground and compare if there is a difference in performance to each other.
    3) If you do see a difference, in step 2, then pick the one that gives better S11 data closer to that in step 1 above.
    4) Based on 3 above, you will need to see if you can retune the matching elements to see if you can get back to a good S11 RL (< -15dBm).
    5) IF you cannot, it means that the metal under the antenna is effecting the antenna performance and you will need to consider a different antenna or move the metal away. Perhaps an option of metal further away with some no-absorbing material below the antenna between the metal to still give you support...not sure if this will work, but just a thought.

    If 5 does not work, then can you use an external antenna?

    Thanks,
    Riz
  • 0 in reply to Rizwan Murji
    TI__Genius 13710 points
    Hi Benjamin,

    I haven't heard back from you. I'm assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has been locked due to time-out)


    Thanks,
    Riz
  • 0 in reply to Rizwan Murji
    Prodigy 140 points

    Hi Riz,

    Thanks for your reply. there was a mix up on the order of the devlopment kit for test so I recieved the kit only Friday. I haven't tested it yet but I will go throught the tests and just go from there. Thanks for you recommendation.

    Ben

  • 0 in reply to Benjamin Couture
    TI__Genius 13710 points
    Hi Ben,

    Your welcome! I will go ahead and close this thread for now. Feel free to re-open or repost as needed!

    Thanks,
    Riz