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CC1310: Component placement and RF performance

marsod
Prodigy 20 points
Part Number: CC1310


Hi,
We are working on a 868 MHz design using CC1310 based on the 4 layer reference design for the small helical PCB antenna. Due to space limitations, we might need to put either a CR2032 coin cell battery holder or at least some part of it, or a push button (or a part of it) just below the CC1310 on the opposite side of the board. What effect on RF performance would any of these alternatives have, do you think? We will use a network analyser to figure out the matching network.
An alternative to this is to have the CC1310 further away from the PCB antenna with the trace either before or after the matching network be longer, approximately 15 - 20 mm (which would be the preferred way here, before or after?). Would that be a better alternative? If so, what would we have to adjust from the reference design except probably the matching network component values.
Any input much appreciated.
/Martin Söderström 
  • 0
    TI__Guru**** 317180 points
    Placing something "under" the CC1310 (on the other side of the board) is normally not an issue. The exception would be if the item was very noisy. In this case the CC1310 with components are RF shielded from what you put on the other side of the board by the ground layer. The placement of the battery/ button with respect to the antenna is more important , they should be as far as possible from each other to not impact the antenna. The matching will be impacted but also the efficiency since anything close to the antenna will absorb some of the signal.

    If you need to increase the trace length, do that after the matching network (where you have a 50 ohm interface)
  • 0 in reply to TER
    Prodigy 20 points

    Thanks! Just to make sure I understand correctly: should the components on the other side of the board from where the RF module is located be placed as far as possible from each other in order to make the least impact on the antenna, or should these components just be as far away from the antenna as possible?

    And just to clarify: no components will be placed under the "keep out" area for the antenna, they will all be completed contained under the ground plane.

  • 0 in reply to marsod
    TI__Guru**** 317180 points
    As far away from the antenna as possible for for components that contain metal and have some volume as batteries etc.