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CC2564MODNCMOET antenna issues

Prashanth Kumar N
Intellectual 470 points
Other Parts Discussed in Thread: CC2564

Hi,

We have designed a BT board based on CC2564MODNCMOET for one of our projects with third party design house. Our third part design house has chosen the following antenna design recommend by TI http://www.ti.com/lit/an/swra117d/swra117d.pdf . With this antenna, we are able to establish connection, but the range is less than 10ft. If the circuit is kept in a enclosure, it drops further.

In parallel, we tried our code on CC2564 Audio sink kit from TI which uses http://www.ti.com/lit/an/swru120b/swru120b.pdf (Invertef F antenna), the range is very good.

After Googling on understanding antenna (quite a complex stuff), i bumped into TI document which says inverted F-antenna has better efficiency but i have seen other

TI modules which uses the same antenna design we have selected.

Now our design engineer is not clear as to what is the issue for losing on range and even i am not sure what to ask or where to debug as i am not HW centric person.

Few things which i have checked and experimented are:

1. Check the schematic given by TI and our schematic, they are both same. Designer has followed reference schematic.

2. Tweak the capacitors values around antenna, didn't show any improvement.

3. Dimension of PCB antenna followed by our designer is same as TI ref design.

4. Lot of articles talk about ground plan can also cause antenna efficiency to come down. I quite didn't get this, but i do see kind of plane around the PCB antenna.

As i have hit a road block, not sure what else to look for. Looking for help on some pointers and how to debug this further. Thanks a lot in advance

Thanks

Prashanth

  • 0
    TI__Mastermind 23565 points
    Hi Prashanth,

    Could you share the gerber files? Did you use a controlled impedance RF trace? i.e. RF trace between MODN and antenna.

    ~Miguel
  • 0 in reply to Miguel
    Intellectual 470 points

    Hi Miguel,

    Thanks for the reply. I don't know much about antennas (trying to understand from past few days, not a easy cup of tea). Attached are gerber files for the BT board which was designed from my vendor. Please have a look at them and provide your expert advice.

    -Prashanth

    BT_Board_PCB.rar

  • 0 in reply to Prashanth Kumar N
    TI__Mastermind 23565 points

    Hi Prashanth,

    Here are couple of comments:

    a) The RF trace does not seem to be an controlled impedance trace. Do you have the design rules used for this trace? Furthermore, the RF trace should be better a completely straight line rather with no little "zig-zag" lines.

    b) According to the antenna design guide, it has already been matched to 50 ohm. So there is no need of external matching components. Have you  tried bypassing the external matching circuit? i.e. L1 = 0ohm resistor, and C5/C9 = DNI.

    BTW, I did not measure the antenna traces BUT I assume you follow the exact same measurements as provided in the antenna design guide.

    ~Miguel