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I am programming a SX126x IC in GFSK modulation.

I am trying to figure out if there is a formula to calculate the bandwidth.

I understand that the BW can be programmable from ~4 to 500kHz.

In the datasheet, it shows me some fixed bandwidth values (they also show the variables from their own library, I am making my library) and I lined them up to try and understand what the formula might be:

sx126x bandwidth

The decimal values range (and all the numbers are here) from 9 to 31. I colored the "pattern."

Is there any mention of the formula for the BW in the datasheet so I can implement it? I think maybe there is a standard formula in the RF world that I am not aware of, and that might be the reason they don't mention it in the datasheet.

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2 Answers 2

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I agree that hardcoding the table is the most appropriate way. But for reference, the formula appears to be approximately:

  • Bits 0-2 of register value: exponent
  • Bits 3-4 of register value: divider

BW = 3.736 MHz / ((divider + 3) * 2exponent)

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  • \$\begingroup\$ Too lazy to validate that now. I will judge you another day. But have my upvote for the effort. \$\endgroup\$ Commented Nov 11, 2023 at 20:19
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It looks like I had to hard-code the BW setting(s). That's how they do it in the official library as well:

sx126x bandwidth

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