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SMARTRFTRXEBK: RSSI and AGC

R S60
Prodigy 70 points
Part Number: SMARTRFTRXEBK
Other Parts Discussed in Thread: CC1120

Hi,

I want to know how the RSSI is calculated in SmartRF Studio, and how changing the AGC register values can alter this calculation. 

It would also be good to know how IF ought to change as data rate is increased. 

Finally, I have a pair of CC1120's and I want to test the relationships between important RF parameters in order to get a better understanding of what the chip is capable of, as well as how it can be optimized for certain qualities.

What independent variables do you suggest I alter, and how inter dependable are they? Last but not least, in a practical sense, what's the best way to approach this is in such a way that I can truly learn about this chip?

  • 0
    TI__Mastermind 36375 points
    RS60,

    The RSSI is calculated inside the CC1120 and provided to the user after the effect of the AGC have been removed. Therefore there is no need to worry about the setting of the AGC for each packet.

    For the rest of your studies I suggest starting with and staying with using the recommended settings inside SmartRF Studio. Then you can modify the settings from there and the tool will warn you in are selecting something that might not or will not work. Do you worry, you cannot damage the device.

    Regards,
    /TA
  • 0 in reply to TA12012
    TI__Guru**** 317180 points
    The use of IF depends on the signal bandwidth. I don't have a good figure (and I didn't find one with a quick google search) showing this so I will try to explain it with words.

    If the analog frontend we have a mixer and the IF frequency is default 62.5 kHz. If this is too low the flicker noise will start degrade the signal, if too high the signal starts getting filtered by the noise shaping of the ADC. In DC the digital post processing insert a filter to remove DC. If IF is used the signal will be centered around the IF frequency. If the signal bandwidth is too large (~80 - 100 kHz) the signal will start to be filtered by the DC filter and the performance will degrade. Then, zero IF has to be used.