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CC1310: CC1310 range issue

shabeeb av
Prodigy 50 points
Part Number: CC1310

Hi,

Below is my attached CC1310 design copied from TI launch pad design.

From the below circuit, i tuned antenna and matched to 50Ohm also measured output power by removing 100pF DC block. Both are good and working as per the settings. 

My issue is by connecting 100pF and when we check range it is coming lower.

But when we keep R3 0Ohm (Antenna not matched 50Ohm or not tuned) the range is better.

Can any one guide me how to address this issue?. Is it necessary match to 50Ohm on Balun side? if yes please advise me how to do this?

The range is reducing from 150meter to 50 meter due to this issue.  

  • 0
    TI__Guru**** 317180 points
    Your results indicate that the antenna is not matched.

    "From the below circuit, i tuned antenna and matched to 50Ohm also measured output power by removing 100pF DC block. Both are good and working as per the settings."
    - What did you measure the output power to?
    - Could you outline exactly how you tuned the antenna?
    - When you did range testing, could you have detuned the antenna by having something close to the antenna or using a different casing than you used when you tuned the antenna?
  • 0 in reply to TER
    Prodigy 50 points
    Thanks for your reply!!

    I set output power 14dBm through SmartRF studio and measured 13.56dBm in spectrum Analyzer.
    For antenna i tuned and measured with enclosure SWR 1.2,S11= -26dB and Z0=48Ohm in network analyzer by removing 100pF and connected pigtail towards Antenna(pi matching input).

    - When you did range testing, could you have detuned the antenna by having something close to the antenna or using a different casing than you used when you tuned the antenna?
    Re: We have used same enclosure, antenna and antenna position same either in tuning and range test.
  • 0 in reply to shabeeb av
    TI__Guru**** 317180 points
    Do you have a picture of exactly where you connected the pigtail? I assume you accounted for the length of the pigtail?

    Everything looks good but the results indicate that the antenna is not well tuned (even though the tuning results looks good) hence it could be the antenna tuning method that causes some issues.
  • 0 in reply to shabeeb av
    Prodigy 50 points
    Please find the attached above snap for the pigtail connection.

    Q: I assume you accounted for the length of the pigtail?
    Re: I couldn't do, could you guide me ? need to characterize as open port?

    do i need to match discrete balun and filter portion to 50Ohm? if yes how do i do this?
  • 0 in reply to shabeeb av
    TI__Guru**** 317180 points
    See chapter 6 in www.ti.com/.../swra161b.pdf

    On the VNA you have on option called "port extension" where you can account for the length of the pigtail.
  • 0 in reply to shabeeb av
    TI__Mastermind 32180 points

    Hi,

    You just need to compensate for the semi-rigid cable whilst measuring your antenna:

    • Disconnect the semi-rigid cable core to the antenna feed point (OPEN)
    • Compensate for the cable length with port extension/s, have the smith chart format on the VNA so you can clearly see that it is OPEN
    • Keep the semi-rigid cable shielding attached to the GND plane of your board.
    • Re-solder the semi-rigid cable core back to the antenna feed point.

    You do not need to match the discrete balun and filter portion to 50 ohm, just as long as you have followed the reference design.

    Regards,

        Richard