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TRF372017 Sideband Suppression

Eamon Nash
Prodigy 10 points

How did you get around the issue of LO harmonics degrading sideband suppression as described in your excellent ap note "LO Harmonic Effects in I/Q Balance and Sideband Suppression in Complex I/Q Modulators?

Eamon

 

  • 0
    TI__Expert 3075 points

    Hi Eamon,

     

    A few things to note are:

    1.) Filter the LO: In order to attenuate the harmonics and prevent this phenomena from occurring, filtering the LO before the modulator is good practice

    2.) Verify the layout: make sure you have 50ohms matching on the LO lines and you have either no (effective isolation between layers) digital noise coupling into the LO lines.

     

    Thanks!

    Carissa

  • 0 in reply to Carissa Sipp
    TI__Expert 3075 points

    To add, specific to the TRF3720:

    1.) Inherent in the design we have maximized this and the SBS is as reported in the datasheet.  SBS with another LO source and modulator can change per different LO source options.

    2.) Within the layout of the chip this is maximized (matching and isolation).  With an external LO source this has to be looked at carefully in the layout of your board.

     

    Thanks!

    Carissa