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Original question:

CC1350: Sub-GHz antenna discrepancy between CC1350 and DN038 antenna dimensions

CC1352P: Sub-GHz antenna discrepancy between CC1310 and DN038 antenna dimensions

Inge Nikolai Torsvik
Prodigy 120 points
Part Number: CC1352P
Other Parts Discussed in Thread: CC1350

Hi,

I was thinking of using DN038 in a new design I am working on. I discovered that there was a difference between DN038 and some development kit, like CC1310EMK and CC1350 Launchpad.

It was stated in this post: e2e.ti.com/.../636230

that the "The DN038 design uses a smaller board than the CC1350 LP and it was found that changing the antenna some for the CC1350 LP the antenna itself is much closer to 50 ohm."

If we end up following the design of DN038 is it always possible to use the matching network to get 50 ohm impedance on the antenna, or is it better to use a design like the CC1350 LP, and then cut away an extra "winding" later if we find that give a closer match to 50 ohm? The board size we are using is 5 x 4 cm.

Thanks,

inge

  • 0
    TI__Guru**** 317180 points
    I would go for both solutions. Use the longest version of the antenna and test if adjusting the length gives a better result. Then tune using the tuning components. For this antenna, the thickness of the board is part of the length of the antenna. Hence if your board has a different thickness than the ref designs this will impact the required matching. If the antenna has an impedance far from the center of the smith chart it's more difficult to adjust the impedance by tuning.
  • 0
    TI__Mastermind 33080 points
    The length of the antenna is dependent on the size of the GND plane. This is the reason why there is a difference in the antenna length between the two designs. When copying a monopole antenna design it is always important to note the size of the GND plane, this is valid for all types of monopole antennas, i.e. chip antennas, wire antennas.
    For the first prototype, it is always good to make the antenna a little bit longer so the length can be tuned exactly for the final product with casing, display etc. Note that the EM designs are plugged into a mother board which also has a larger GND.

    Regards, Richard
  • 0 in reply to RGW
    Prodigy 120 points

    Thank you. This was very useful, I will add an extra length on the antenna, and tune it when I get the PCBs.

    I am also using DN007 on my PCB design. Would you recommend using longer antenna there as well? If that is the case, how much would you extend?

    Best Regards

    Inge

  • 0 in reply to Inge Nikolai Torsvik
    TI__Guru**** 317180 points
    The wavelength for 2.4 Ghz is close to to 3 times shorter than for 868 MHz which makes 2.4 GHz antennas much less sensitive to the ground plane size and hence the 2.4 GHz antennas could be in most cases be copied from the reference design without modifications. You would still need matching components since the resonance frequency of the antenna could shift due to the casing etc.
  • 0 in reply to TER
    Prodigy 120 points
    Thank you! I have included the matching network.