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What's the consequence of changing the PLL bandwidth on CC1020?

Timothy Bedford
Prodigy 20 points
Other Parts Discussed in Thread: CC1020

I'm not clear on the consequence of changing the PLL bandwidth.

Does the PLL bandwidth need to exceed my baudrate? Or should it exceed my frequency deviation? Or should it exceed my channel width (or channel spacing)?

What happens if the bandwidth is too low? Do I lose a little bit of sensitivity, or a lot? Do I lose the ability to "acquire" the carrier in the first place (but once I have, does the bandwidth still matter)?

What happens if the bandwidth is much higher than I need? Do I lose a little bit of sensitivity, or a lot? Does the receiver then become susceptible to adjacent channels?

Thanks in advance.

  • 0
    TI__Mastermind 39860 points

    CC1020 uses in-loop modualtion and there is a lower limit to the PLL bandwidth given by the symbol rate. If the bandwidth is too low you will start filtering the data. That is, the frequency deviation on-the-air will be lower than what you program into CC1020. On the other hand, the PLL bandwidth should be as low as possible to minimize phase noise. Phase noise is an issue both in receive (selectivity, ACR) and transmit (ACP, occupied bandwidth).