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CC2640R2F: Bluetooth RF Range Comparison of a 4 Layer PCB Board vs 2 Layer PCB Board?

Markel Robregado
Guru 86865 points

Part Number: CC2640R2F
Other Parts Discussed in Thread: CC2650

Hi,

    I have read here that a BLE 4 Layer PCB Board has better RF due to more Layers for grounding. So, does the BLE 4 Layer PCB Board would have better RF range compared to a BLE 2 Layer PCB Board?

-kel

  • 0
    TI__Guru** 106705 points
    Hi Kel,

    The key care-about here is grounding which is critical for RF performance. On a 4-layer PCB it is relatively easy to achieve good grounding since a whole PCB layer can be dedicated only to ground plane.

    If you are careful with the layout on a 2-layer PCB it is still possible to get comparable performance to a 4-layer board. An example for this are all the CC2650EM reference designs which are all 2 layer. The CC26xx LaunchPads are 4-layer, but that is mostly to simply all the signal routing. The RF performance between these are comparable.

    On CC13xx running sub-1 GHz at higher output power, the requirements for good layout are even stricter, and I would only recommending using PCBs with a full solid ground plane for those devices.

    In the end, it is all about how careful you are with your ground connections. The difference between a well designed layout and a poorly designed layout may manifest itself in range, but typically it will first and foremost lead to reduced RF performance in terms of higher spurious emission which will violate regulatory requirements.

    Regards,
    Fredrik
  • 0 in reply to Fredrik K
    Guru 86865 points
    Hi Fredrik K,

    Thanks for your detailed reply. I am current doing firmware for a custom CC2640R2F 2 layer PCB board. The RF range is very short compared to CC2640R2F Launchpad. The custom CC2640R2F 2 layer board was not designed by me. Can I ask you to review our PCB design and give us advice to improve it, through Private Messaging. I will send you a friend request.

    -kel
  • 0 in reply to Markel Robregado
    TI__Guru** 106705 points
    Hi Kel,

    What you describe is often due to poor antenna matching. Do you know if the antenna impedance has been measured and tuned?

    General design guidelines can be found in this document: www.ti.com/lit/pdf/swra640

    Regards,
    Fredrik
  • 0 in reply to Fredrik K
    Guru 86865 points

    Fredrik K said:
    Do you know if the antenna impedance has been measured and tuned?

    No. I will ask the PCB Designer.

    The PCB design is based from CC2650 uTag. It has 2 analog sensors and 1 I2C LSM303AGR Sensor. The antenna is Single Ended RF. Just looking at it there are lots of spaces in between traces, so I guess there are not much grounding, which will affect RF. We will share PCB design files for review through Private Messaging.

    -kel

  • 0 in reply to Markel Robregado
    TI__Guru** 106705 points
    Another thing to keep in mind is that the antenna performance is also dependent on the ground plane (for most chip- and PCB antennas, not dipole antennas). Smaller boards with smaller antennas will thus have lower antenna efficiency and shorter range than larger boards with larger antennas. It is expected that the uTag has shorter range than the LaunchPad.

    What range do you actually get from the board, and what is your requirement?
  • 0 in reply to Fredrik K
    Guru 86865 points
    Hi Fredrik K,

    With the custom CC2640R2F board based on CC2650 uTag, I am connected at the 2nd floor of our house, I go down to first floor living room and it disconnects.

    With the CC2640R2F Launchpad, I am connected at 2nd floor of our house, I go outside our house walking down the street and it is still connected.

    -kel
  • 0 in reply to Markel Robregado
    TI__Guru** 106705 points
    Hi kel,

    I have not seen the design files yet, but for a very small design, not being able to connect between multiple floors may be expected.

    Regards,
    Fredrik