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CC1120: Test Setup for testing receiver saturation on the CC1120 versus CC1101

Sudesh Sheodass
Intellectual 680 points
Part Number: CC1120
Other Parts Discussed in Thread: CC1101,

Hi,

We are running tests a proprietary mesh network were the nodes are co-located all in the same room, mounted right next to each other. Our nodes maybe either Co-ordinator Devices (CD), Full Function Devices (FFD) or Sleepy End Devices (SED). Saturation is a big problem in this use case. We have prototypes built using the CC1101 and due to the CC1120 providing better saturation handling, we are changing our design to incorporate the CC1120. This is based on iour questions on this post: https://e2e.ti.com/support/wireless_connectivity/proprietary_sub_1_ghz_simpliciti/f/156/p/598533/2200421#2200421 

We want a test setup that can compare the saturation when using the CC1101 versus the same setup using the CC1120.

1. Can TI provide some guidance on how to setup such a test? 

2. Is there sample code to test saturation?

regards

Sudesh

 

  • 0
    TI__Guru**** 317180 points
    We only do conducted measurements to test this.

    We do PER vs level measurements where the input signal is stepped in 1 dB steps from 10 dB below the sensitivity limit to 10 dBm. If the chip saturate the PER goes up. We do this testing in a labview environment where everything is automated. (The code is specially tailored for our lab and will not work anywhere else)

    If you want to compare saturation you can do it by have a splitter splitting the in signal to the CC1101 and CC1120 boards. You can have a known signal source with programmable attenuation between the generator and the splitter and confirm that the CC1101 start loosing packets for high signal level and CC1120 not.
  • 0 in reply to TER
    Intellectual 680 points
    Hi There,

    Just following up on this thread again with a few more questions:
    I am in the process of setting up a saturation test for the CC1101 (while I still await completion of our boards for the CC1120), however, I do not have a signal generator to feed in the signal. Rather, I want to use one CC1101 board as the transmitter, and have a number of CC1101 boards as receivers, stacked together. I will use the transmitter to send packets periodically and monitor the PER on the receivers.

    My questions is:
    1. Will this test setup work with reasonable accuracy? It does simulate the live environment where the system will be deployed, hence I want to test it like that.
    2. In order to change the TX power from 10 dB below the sensitivity limit to 10 dBm, what is the sensitivity limit to start with?
    3. How can I dynamically change the power level on the transmitter in 1 dB steps? I.e. What would be my PATABLE[0] setting be for each of the 1 dB steps from 10 dB below the sensitivity limit to 10 dBm? Note, I am not using ramping - I just want to manually adjust the TX power in 1 dB steps at run time.

    Regards
    Sudesh
  • 0 in reply to Sudesh Sheodass
    TI__Guru**** 317180 points
    I define saturation as where the RSSI readout saturate (The RSSI read remains the same even if the input signal increases) but when I read your post again it could look more like you want to improve blocking.

    Could you elaborate more around which parameter (and why) you are interested in?
  • 0 in reply to TER
    Intellectual 680 points

    Thanks for clarifying about how you define saturation. I'm not familiar with blocking, as I don't have much hands on RF experience. However, from doing some quick reading  on the web and reading about the definitions of selectivity and blocking in the document "Performance_Line_Introduction.pdf" mentioned in this post: https://e2e.ti.com/support/wireless_connectivity/proprietary_sub_1_ghz_simpliciti/f/156/p/578792/2125027, it seems that our use case would require both good selectivity and good blocking performance.

    With a number of our devices (even up to a good few hundred) stacked next to each other in some installations, we want both the ability to filter out interference caused by this close proximity were the devices would be operating a set of 5 fixed channels chosen randomly, as well as interference from outside frequencies. We also want the devices (who maybe transmitting or receiving at any given time) to ideally, not saturate at higher input powers, such that they fail to transmit/forward packets within a given amount of time, breaking the network.

    I hope this makes sense!

    regards

    Sudesh

  • 0 in reply to Sudesh Sheodass
    TI__Guru**** 317180 points
    If you have a few hundred nodes using 5 channels you should use LBT or similar to ensure that not multiple nodes close to each other tries to use the same channel.

    As you can see from the datasheet number, CC1120 has better selectivity and blocking than CC1101 and will give better performance in a busy RF environment than CC1101. In the end the best way to test this is with a test network with a lot of nodes. To get the best performance it could be a thought to assign nodes that are close to channels as far away as possible to get the best blocking.