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Need a RF "Subtractor" / RF Instrumentation Amplifier

bd12976
Prodigy 20 points

 

I need to isolate the difference between two signals.  The signals are at 3.5 GHz, but I would be interested to hear any information on ICs that would perform similar functions at frequencies anywhere over 1 GHz.  From my own research, an instrumentation amplifier seems to be exactly what I am looking for (in that it has high input-impedance and differential inputs) however no commercially available products that I can find have anywhere near the desired bandwidths.  Does anyone have any ideas or suggestions that could put me in the right direction?

One option I am considering is looking into using a differential amplifier (likely intended as an ADC driver) with a transformer to convert the differential output to single-ended.  However, my concerns here are input-impedance and the introduction of parasitics when attempting to connect these high frequency components.

Thank you for your time.

  • 0
    TI__Intellectual 1275 points

    bd,

    Our operational amplifiers would not work up in the 1 GHz + range. From you description, it sounds like you need something like a 180 degrees RF combiner, such as this one from Minicircuits:

    http://www.minicircuits.com/pdfs/ZAPDJ-2.pdf

    This would output the different between the two input signals, to the level of amplitude and phase matching provided by the combiner.

    If your signal BW is on the order of 100 MHz or less, you could consider downconverting the signal to a lower frequency like 200 MHz using two mixer and a shared LO, and  then using an operational amplifier to output a  signal that would be the difference between the two signals. However, you would like encounter poorer matching through the down conversion process than that provided by a 180 degree RF combiner.

    Robert

  • 0 in reply to Robert Murano
    Prodigy 20 points

     

    Thanks for your help.

  • 0
    Prodigy 25 points

    i want to know  where i wil find software of CMD5016.exe , buy?  my email is  qibo15193@126.com  thank you for your time  contact me  , 

    Thank you again

  • 0 in reply to bo qi
    TI__Mastermind 37500 points

    Hello,

    The cmd5016 DOS terminal application that runs under Windows, is free for download  at  http://focus.ti.com/docs/prod/folders/print/gc5016.html.

    The tool name is CMDGC5016 Standard Configuration Programming Tool.

    There is a Guide for using CMD5016 at the same web-link.  It is named GC5016 Configuration Guide. 

    There are special testing configurations for the GC5016 a diagnostic test (checks internal function, uprocessor register programming, clock) [GC5016 Diagnostic Configuration File]; and a Bypass test which replicates the Ain to the Aout port [Bypass Configuration for GC5016]. 

    Regards,

    Radio Joe