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CC2652P: Poor coverage. Maybe the matching network is wrong?

Massimo Capozza
Prodigy 10 points

Part Number: CC2652P

We are struggling with an existing design based on CC2652P1FRGZR. We have an evaluation board that works fine, while the attached schematic diagram provides very poor coverage (i.e., the maximum distance where the signal can be detected and a connection can be established is just a couple of meters).

Our first guess was that the RF switch S2 was not correctly set. However, we checked all possible configurations of it, and it seems that it's not the root cause of the problem.

We noticed that the matching networks used (L2, L5, L6, C41, C45, etc.) have quite different values with respect to the values we find on the evaluation board or on other schematic diagrams. The person who designed this schematic diagram a couple of years ago does not remember which reference design he used. So, we wonder if the matching network of the attached schematic diagram is correct. If the tuning of the network is completely wrong, this would definitely justify the problems that we are experiencing.

Can anyone help?

  • 0
    TI__Expert 7120 points

    Hi Massimo,

    Are you trying to achieve 10 or 20dBm at the output? The filter value you have shown is for 10dB. If 20dBm is your target output power use the CC1354P-2 reference design.

    Best regards,

    Bun

  • 0 in reply to Bun Kuch
    Prodigy 10 points

    Hi Bun,

    Thank you for your reply.

    As far as I understand, the CC2652P has a TX-only output (e.g., as a beacon) with up to +20 dBm output power, and a TX/RX interface that can transmit up to +10 dBm. We have implemented both interfaces in our design, although the TX/RX interface is the one that is most interesting for us. Could you please confirm that the filtering networks used in the schematic diagram that I attached are OK?

    We initially thought that we were not setting the antenna switch (S2) correctly, although I think that we tested all possible configurations. If the filtering networks are OK, what else can be wrong?

    Massimo

  • 0 in reply to Massimo Capozza
    TI__Expert 7120 points

    Hi Massimo,

    For 10dBm, your filter value looks correct. Please add "pigtali" after C53 and measure the output power. This will immediately tell you where the problem lies.

    Best regards,

    Bun

  • 0 in reply to Bun Kuch
    Prodigy 10 points

    Hi Bun,

    C53 is on TX-only branch of the circuit. What about the TX/RX branch (i.e., the one with C42 in lieu of C53)? Are the values of the filtering network correct for that branch?

    Massimo

  • 0 in reply to Massimo Capozza
    TI__Expert 7120 points

    Hi Massimo,

    The same logic apply to the TX/RX path. Use the CC1352P-4 filter values for 10 dBm output and CC1352P-2 for 20dBm. Yes, please add a pigtail after C42 and measure the output power, which will tell where problem lies. To answer your answer, the filter values for 10dBm on the TX/RX path is incorrect based on the CC1352P-4 reference design.

    Best regards,

    Bun