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TRF370417: Side band suppression

Charan MMJ
Prodigy 90 points
Part Number: TRF370417
Other Parts Discussed in Thread: DAC12DL3200

Tool/software:

Hi,

We are using DAC12DL3200 for generating I & Q signals. These I & Q signals are upconverted using TRF370417. We are getting a maximum sideband suppression when the phase difference between I and Q is maintained at 94 degrees. Our query is:

1. Do we need to adjust phase for all the boards individually?

2. Does this phase adjustment value vary from component to component?

3. According to the datasheet, we should be getting max sideband suppression when phase difference between I & Q is 90 degrees. But why are we getting max suppression at 94 degrees.

Thanks in Advance.

  • 0
    Prodigy 90 points

    Hi,

    Is there any update on this.

  • 0
    Prodigy 90 points

    Hi team,

    Any update on this?

  • 0 in reply to Charan MMJ
    TI__Intellectual 1910 points

    Charan,

    Sorry for the delay... We are looking into this, and will get back soon.

    Keyur

  • 0
    Prodigy 90 points

    Hi Keyur,

    Any update?

  • 0 in reply to Charan MMJ
    TI__Expert 4510 points

    Hi Charan,

       Kindly give us time till Monday. We will circle back.

    Thanks and Regards,

    Hruday

  • 0 in reply to Charan MMJ
    TI__Expert 4510 points

    Hi Charan,

       Thanks for your patience.

    The sideband suppression of the TRF370x can be optimized by adjusting the amplitude and phase balance between the quadrature inputs. The ideal condition is when (I,  Q,) have exactly the same amplitude and the phase relationship is: I = 0°, Q = 90°. Using an iterative procedure, the gain and phase balance can be adjusted to achieve suppression levels that exceed 60 dBc. The level of suppression observed depends on the amount of resolution available from the source driving the modulator.

    1. Yes you may need to adjust phase on all boards individually to get the maximum suppression based on pcb and device variance.

    2. Yes it may change from component to component. It depends on I and Q mismatch of DAC, Modulator and pcb traces.

    3. In ideal scenario we should get max suppression at phase difference of 90 degrees and equal amplitude. But remember that Phase and Amplitude imbalance of components will vary.

    Regards,

    Hruday

  • 0 in reply to Hruday Kumar Mudireddy
    Prodigy 90 points

    Hi Hruday,

    Thank you very much for the reply.

    As per datasheet, maximum side band suppression will be ~50dBc. For few frequencies we are not able to get suppression more than 30dBc. We tried changing the phase between I and Q and also changing voltage ration between I and Q, still no improvement.
    Please suggest is there anything else that can improve my side band suppression.
  • 0 in reply to Charan MMJ
    TI__Expert 4510 points

    Hi Charan,

        At what frequencies are you seeing <30dBc suppression. Also are you measuring this on EVM?

    Regards,

    Hruday

  • 0 in reply to Hruday Kumar Mudireddy
    Prodigy 90 points

    Hi Hruday,

    We are using our custom board for measuring.

    When we are using LO frequency of 2024.5MHz and IF of 400MHz and 500MHz, we are observing side band suppression lesser than 30dBc.

    Thank you.