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TRF370333 LO Inputs

Elina Senkevich
Intellectual 315 points
Other Parts Discussed in Thread: TRF3765, TRF370333

Hello All,

Please advise if there is any advantage by feeding the LO inputs of TRF370333 differentially. In datasheet there is no reference regarding this issue. The customer is using  TRF3765 as LO source and is considering to use the differential outputs. Any application note or recommendation would be very helpful.

Thank you.

Regards,

Elina

  • 0
    TI__Intellectual 1650 points

    Hello Elina,

    When done properly we have not seen a difference in performance between single ended on differential LO's on the TRF370333.

    The TRF3765 does have an app note that discusses different terminations and filters.
    http://www.ti.com/lit/an/slwa070/slwa070.pdf

    The TRF370333's internal LO network is a poly-phase network to shift LO I/Q legs to 0/90 degrees. This LO network is sensitive to harmonics on the LO, as described in this app note http://www.ti.com/lit/an/slwa059/slwa059.pdf. This app note shows how the harmonics on the input of the TRF370333 affect the sideband suppression. If the customer is using the output dividers (/2, /4 or /8) of the TRF3765, then this has the affect of squaring up the TRF3765 output signal. This squaring up of the LO signal causes higher LO harmonics at the input of the TRF37033. In this useage case and if the customer is concerned about sideband suppression, then we recommend a low pass filter on the LO path between the TRF3765 and TRF3703 to lower the LO harmonics seen at the input of the TRF370333.

    Thanks
    Chris

  • 0 in reply to Chris Pearson
    Prodigy 100 points

    Hey Chris,

    Thanks a lot. The info is very useful.

    Best Regards,

    Daniel