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Designing a four layer stack up PCB having nrf52832 SoC with chip antenna

Discussion in 'PCB Layout, Design and Manufacture' started by Vansica, Jan 5, 2018.

  1. Vansica

    Vansica

    1
    0
    Jan 5, 2018
    I am designing a four layer stack up PCB having nrf52832 SoC with chip antenna (2450AT18B100 Johanson Technology).It is BLE Board (2.45 GHz). This is the first time I have been designing a PCB with an antenna. I am using kicad EDA Software. The stackup of my design is:

    1. Signal and RF traces with ground copper fill (Green Colour in Picture below)
    2. Ground Plane
    3. 3.3V Plane
    4. Bottom Plane (Basically Solid Ground Plane) (Red colour in Picture below)

    I am going to add many vias (at 1/12 of RF frequency which will be 2.45 GHz). The antenna part is not completed yet because I am yet to receive some specification from my PCB fabrication house. I will change the width and shape of antenna feed considering the distance between signal plane and ground plane. I have one question regarding the calculation of width of antenna feed line. Since, I have four layers, Can I use formula of coplanar waveguide with bottom ground plane? Won't power plane and bottom layer will effect the impedance of coplanar waveguide? Do I need to take into account presence of power layer and bottom layer (actually solid ground plane).

    NOTE: The other sensor in the left part of my layout is a CCD (TCD1304) which is basically a linear image sensor.(CCD image sensor application)

    What I want from the community is suggestion on the pcb and review my design for RF. Since, this is the first time I have designed such a board, I don't want to design a PCB which won't work or work with very short range. The pictures of my PCB are given below:

    Picture 1:
    jDbqw.png
    Picture 2:
    cOM1J.png
    Picture3:
    SXrxN.png
    After reviewing the datasheet of my chip antenna and suggestions from Johanson Technology, I can see they have suggested a large ground plane for which I don't have space.You can check pictures of my layout above as I have marked area for antenna (7mm X 23mm).

    The picture below are taken from Johanson Technology's layout suggestion:
    LAczw.png

    wI1iJ.png
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,078
    Dec 18, 2013
    Turn your antenna and associated components through 180 degrees so the feed line from L1 is straight. Use this from my calculator to help you with your layout for the feed line.
    Thanks
    Adam

    co-planer.PNG
     
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,078
    Dec 18, 2013
    Show us the circuit diagram please. The rest of the circuit looks not too bad (waiting circuit diagram) You have some acid traps that need sorting also. I let you find out what that means :)
     
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