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RTOS/CC1350: Receiver saturation

ChaDissa1931
Prodigy 55 points
Part Number: CC1350

Tool/software: TI-RTOS

I am using the CC1350 Sub 1GHz mode, with a RFID reader which is also operating on the same band (902 to 928MHz). 

I am trying to use the CC1350 and RFID on different channels.

In CC1350 datasheet it is mentioned that the Receiver saturation is 10dBm.

I need to use the RFID reader with a transmit power of 2300cdBm(23dBm)
The CC1350 receiver is located about 5cm away from the RFID antenna.

However even when I set the RFID antenna to operate in a different channel than the CC1350 operates, the CC1350 dose not receive packets properly?
Could this be becaues of the cumulative power of all channels in this band is more than 10dBm and the CC1350 becomes saturated?

If this is the case, what are the solution that I have?

  • 0
    TI__Guru**** 317180 points
    10 dBm is max to avoid damaging the LNA on CC1350. Are you able to measure with a spectrum analyzer how strong signal you get in on the CC1350 antenna?

    How wide channels do you use? If you look at the selectivity numbers in the CC1350 datasheet you have to have a very strong wanted signal not to be blocked by the RFID signal even if the signals are 1 MHZ apart.

    Assuming 1 MHz between the RFID and the CC1350, CC1350 receives 10 dBm blocker. Then the wanted signal has to be at lease -50 dBm or stronger for CC1350 to be able to receive.
  • 0 in reply to TER
    Prodigy 55 points

    Thank you for your quick response.

    I do not able to find a spectrum analyzer so what I did was, set the CC1350 as a channel analyzer. Do the energy scan for all the channels and record the data. As I mentioned earlier the RFID scanner set to work on another channel group in frequency hopping mode. So the channel scanner shows the peaks in those channels and no power indication to the other channels. Even thought there is another free channels the receiver does not receive the data properly.

    Blue circle shows the Launch pad transmit power, even though it shows quite high power the RX parameters were very low like 50% packet loss. Please let me know if we can have any addition option to overcome that issue.

    I have an idea to change the input to the antenna pin with the ability to band pass the relevant channels and block the channels that the RFID operational channel group. Is this method will work. Or any other method. 

    I used Smart RF studio with two launch pads. One transmitted using 14dBm, 50kbps and channel with 921MHz center frequency. Please let me know if you need any additional information.

  • 0 in reply to ChaDissa1931
    TI__Guru**** 317180 points
    Without having the more exact dBm numbers I find it difficult to comment on if you should have been able to receive. Even if the chip supports up to +10 dBm the RSSI reading saturate around -10 dBm meaning that if you have a stronger signal in than -10 dBm the RSSI will still show -10 dBm.

    Based on the numbers from your previous post it sounds like you would need filtering to increase the blocking.
  • 0 in reply to TER
    Prodigy 55 points

    So if we want to uses a filter, how could we implement that? Is there any documentation to follow? or any design guidelines.
    Thanks again for your response and those are very much valuable to me.