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TRF370417: Output power flatness

Mark Whittington
Intellectual 460 points
Part Number: TRF370417
Other Parts Discussed in Thread: DAC38RF82, DAC5682Z

How can I determine what the expected output power flatness should be for a given LO and baseband bandwidth?  Should I add the contribution from the baseband flatness shown in the following pdf  ( http://www.ti.com/lit/ug/tidu579/tidu579.pdf

  • 0
    TI__Mastermind 18065 points
    Effectively yes. The overall flatness will be a combination of the BB flatness (due to the input BB roll-off) and the RF output flatness (due to the RF output circuit). --RJH
  • 0 in reply to RJ Hopper
    Intellectual 460 points
    To clarify. If I have a BB bandwidth of say 500MHz and an LO of 4GHz, I would take the Pout vs Frequency chart in the datasheet and look at the Pout slope from 3.5 to 4.5GHz and then combine that with the baseband gain slope? It isn't obvious to me that a signal at 100MHz and an LO of 4GHz will have the same RF gain as as a signal at 200MHz and an LO of 3.9GHz.

    Thanks.

    Mark
  • 0 in reply to Mark Whittington
    TI__Mastermind 18065 points
    Correct on both assessments. You are right that the gain at 100 MHz BB + 4 GHz LO is not necessarily the same as 200 MHz BB and 3.9 GHz LO. The data over LO in the datasheet was taken with the BB fixed at about 5 MHz. The data in the app note was taken by sweeping BB input while simultaneously decreasing LO frequency at the same rate so that the RF frequency is kept constant. You can superimpose the gain response of each to get a composite performance for your applications. ---RJH
  • 0 in reply to RJ Hopper
    Intellectual 460 points

    RJ,

    Do you have or can you get data that measures the baseband response out to the specified part maximum of ~1GHz?  Or in lieu of that, do you have some idea whether the performance is significantly different than what I would extrapolate from the app note data?

    Thanks.

    Mark

  • 0 in reply to Mark Whittington
    TI__Mastermind 18065 points

    The app note data is a combination of the DAC output performance + the TRF3704 device.  I think the sharp roll-off at 600 MHz is dominated by the DAC at the given mode of operation.  I recall that we did testing a long while ago with the TRF370x + the DAC5682Z to showcase operation out to 1 GHz (3 dB down).  Enclosed is a design that showcases the TRF3704 with the DAC38RF82 for operation with wide bandwidth signals.

    Short answer: I do not have specific data with isolated performance of the modulator out to 1 GHz offset.

    --RJH

    High Bandwidth Zero-IF Solution for Microwave Backhaul_Final.pdf