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CC1200: About the use of the 137MHz--158.3MHz band

user4117338
Prodigy 30 points
Part Number: CC1200

I directly used the 169MHz recommended circuit, changed the digital register frequency value, and found that its sensitivity dropped by 3 db relative to 169MHz.

It is not advisable to directly send a 169MHz circuit from 137MHz to -158.3MHz.

 

Can the original factory provide an accurate 137MHz--158.3MHz recommended circuit to me?

  • 0
    TI__Guru**** 317180 points

    TI has not not made a reference design for this frequency range. 

    When you test sensitivity on your board, do you get the expected performance on 169 MHz? I would assume that you see a difference between 137 MHz and 158 MHz? 

    You could try to adjust the component values with a factor that is 169/145 to see if that improves the sensitivity.

    You should also evaluate the harmonics in TX and check if these ends up in a restricted band or similar. If that is the case it's possible that the filtering has to be changed. 

  • 0 in reply to TER
    Prodigy 30 points

    If I directly replace the hardware matching circuit of the receiving (LNA_P, LNA_N) with the integrated baluns, consider the factors such as impedance matching.
    Can you recommend a balun for me?


    My need is to use 140mhz, 169mhz, 420mhz directly. General purpose hardware.

  • 0 in reply to user4117338
    TI__Guru**** 317180 points

    These transformers looks like are 50 ohm in/ 50 ohm out, the optimal load impedance for the PA is not 50 ohm. I don't know the optimal load for the frequencies in question since we haven't measured it. Hence the best suggesting I have was presented in the last post.