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Antenna signal problem on CC1101

user5979525
Prodigy 70 points
Other Parts Discussed in Thread: CC1101

Hi everyone,

I am using a CC1101 chip in order to communicate in the 868Mhz band. The digital part seems to be fine, the init is fine and every communication is successful.

Troubles start when I try to send something over the air. The chip reply "successfull send" however nothing happen on the dongle. I had a look on the antenna signal RF-N and RF-P and I realized that when I send the message the voltage goes from about 1Volt to 0 and then goes back very slowly (about 8seconds) to 1V.

I checked every single elements after the RFs pins and they are all good. I checked the power supply (3.3V on digital and analog part) and it does not drop at any time. All power supply pins are correctly tied to the 3.3V supply.

I really don't know what to do to make it work. Any advice would be more than appreciated !

Thanks a lot,

Sébastien

  • 0
    TI__Guru** 106705 points

    Hi Sebastian,

    A multimeter or even an oscilloscope is not the right tool for debugging RF signals. You must use a spectrum analyzer to verify that your radio is working as expected. You can also try controlling your devices through SmartRF Studio to rule out any SW problems.

    /Fredrik

  • 0 in reply to Fredrik K
    Prodigy 70 points

    Hi Fredrik,

    Thank you for quick reply. I don't have this kind of tool, but I know that it would be better. However, do you think the signal behaviour is right, even with an oscilliscope? I did the same on another board with the same hardware (CC1101, same passive component on the antenna line) and the signal goes from 0 to 1V very quickly. On top of that, the chip replies with "SEND_SUCCESSFUL" so I guess this is not a software problem.

    I also tried with another software that is currently running great on another board and I have the same problem.

    Please, give me a clue!

    Thanks a lot.

    Sébastien

  • 0 in reply to user5979525
    TI__Guru** 106705 points

    It is impossible to debug this without more information. Is this a custom PCB you have made yourself, or it is an evaluation board? Are we talking about one single failing unit or several units?

    Fredrik

  • 0 in reply to Fredrik K
    Prodigy 70 points

    This a custom PCB. We designed it based on another custom PCB of a product that is working well. The only difference is the voltage regulator of the CC1101 (independant from the rest of the circuit), the one on the new PCB is a LT1129, fixed output 3.3V. It is supposed to deliver 700mA maximum (well above what is needed).

    I have 2 prototypes of this product (both of them have the same hardware) and they have the same problem. I will bypass the regulator and test with an external power supply.