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Impedance Mismatch at 868MHz

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  • Impedance Mismatch at 868MHz

    I have a designed a board(Sub GHz Transceiver) which is to operate at 868MHz. I followed the Antenna Matching/Tuning circuit which was given by the Controller IC as well as from the Antenna Manufacturer at the Antenna side.
    The Data sheet mentioned Matching circuit(Series5.6pF and Shunt 1.8pF Capacitances) for the range between 866-915MHz.

    But when I checked through the Spectrum Analyzer it was noticed that It's not matched to 50 Ohm at 868MHz instead it showed 40Ohm at 815MHz.
    Can someone guide me to calculate the Series and shunt capacitances
    PS: am not an antenna expert.

    Attached Files

  • #2
    Hi, expecting some answers.
    @robertferanec can you please guide ?


    • #3
      I am not expert in this ... I do not work with antennas much - I only follow design guides.


      • Lakshmi
        Lakshmi commented
        Editing a comment
        I followed the design guidelines but stil...

    • #4
      This company has good information on using antennas, especially in their product data sheets. Sorry I can't be more specific.
      Antenova is a leading provider of high performance antennas and RF solutions for wireless M2M, IoT and consumer electronics. Get in touch with us today for design support and antenna solutions.


      • Lakshmi
        Lakshmi commented
        Editing a comment
        Thanks for your suggestion.
        But now design has been completed and we have working PCB on hand.
        So now changing the design will be critical.
        I agree with you that Antenova has Good support.
        Thank you.

    • #5
      Haven't done much antenna design, but in the datasheet you send it specifically says a range and that it is heavely depended on your own design.
      layerstack substrate / copper thickness comes in to play here and i think it is usual that you would have to tweak it a little by playing with the values ..
      just try and see what values get you were you want.. you might have to go up and down to figure out your best match...

      my question to you is .... does it work? @40Ohms.. or not.. ?

      on a personal note (and with no disrespect) i do not like the " hi expecting some answers " remark..
      we are all here to help were we can, but it is all done in our own "free" time.. just like you try to help others on this forum, but you cannot be demanding anything.
      every design has it's own complications and it would be great if all questions can be answered here..but if there is no expertize on it on this forum you probably won't get any response.
      and i would rather have no advice than bad advise.. But that is me persoanlly.. i cannot speak for anybody else.