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AD9874 BAND-PASS SIGMA-DELTA

Hi, I am building radio SDR for graduation work and I use  AD9874.
Part of my down-conversion is AD9874 and my IF2 frequencies should by 0. Ad9874 has BAND-PASS SIGMA-DELTA with two resonator, external LC and internal RC . When my IF2 should by 0, I don't needs resonators.
Can I turn off internal RC resonator ?
Tell my when I wrong thing

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  • Hello,

    Please read datasheet carefully since it describes in great detail how the AD9874 works.  I would also advice you to look at the AD9864 datasheet that has been recently updated and provides good examples on the SPI initialization boot sequence.

    That said....................AD9874 is based on a super-het radio design with the 1st IF being at the IF input of the device and the 2nd IF being centered exactly at FCLK/8.   Both the LC and RC resonators are tuned such that they are centered at FCLK/8.  The LC external values should be chosen to support the tuning of the LC resonator.

    Regards.

Reply
  • Hello,

    Please read datasheet carefully since it describes in great detail how the AD9874 works.  I would also advice you to look at the AD9864 datasheet that has been recently updated and provides good examples on the SPI initialization boot sequence.

    That said....................AD9874 is based on a super-het radio design with the 1st IF being at the IF input of the device and the 2nd IF being centered exactly at FCLK/8.   Both the LC and RC resonators are tuned such that they are centered at FCLK/8.  The LC external values should be chosen to support the tuning of the LC resonator.

    Regards.

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