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  1. #1
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    True Large Signal Differential Input Impedance Evaluation

    I want to measure differential mode input impedance of true large signal differential driving.

    Target frequency is around 1GHz.

    How can I do this task ?

    I don't mean conversion from large signal single-ended driving like following.
    {S11, S12, S21, S22} -> {Sdd, Sdc, Scd, Scc}
    Last edited by pancho_hideboo; 6th March 2017 at 13:52.

    •   Alt6th March 2017, 13:42

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    Re: True Large Signal Differential Input Impedance Evaluation

    Small bandwidth measurements can be best made with a coaxial cable balun http://www.edaboard.com/thread291529.html#post1246877

    What is large signal for you? Is it in the output level range of usual network analyzers?



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    Re: True Large Signal Differential Input Impedance Evaluation

    Quote Originally Posted by FvM View Post
    What is large signal for you? Is it in the output level range of usual network analyzers?
    Yes, 10dBm at most.



    •   Alt7th March 2017, 12:45

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    Re: True Large Signal Differential Input Impedance Evaluation

    It seems we can measure true large signal differential S-parameter by Advantest R3860A VNA.

    Advantest R3860A VNA have second signal-generator.
    However Advantest stopped development and selling VNA.

    Is there any VNA which can do same task ?



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    Re: True Large Signal Differential Input Impedance Evaluation

    The Advantest obviously does what you explicitly excluded in post #1, calculating the differential impedance from a two port measurement.
    I don't mean conversion from large signal single-ended driving like following.
    If you only need the input related network parameters of the fully differential amplifier, most VNA should be able to doe the same measurement.

    I still believe however, that a balun can achieve comparable or even better accuracy.

    - - - Updated - - -

    O.K., I see the difference. To mimic as large signal differential drive, the VNA must excite both ports 180° out-of-phase. Is this what the Advantest device does?



    •   Alt1st April 2017, 08:55

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    Re: True Large Signal Differential Input Impedance Evaluation

    Quote Originally Posted by FvM View Post
    The Advantest obviously does what you explicitly excluded in post #1,
    calculating the differential impedance from a two port measurement.
    Wrong.

    Quote Originally Posted by FvM View Post
    O.K., I see the difference.
    To mimic as large signal differential drive, the VNA must excite both ports 180° out-of-phase.
    Is this what the Advantest device does?
    Correct.

    Again see block diagram of http://www.edaboard.com/attachments/...401-121913.png

    I also attached block diagram of conventional 4-Ports-VNA.
    I have two 4-Ports-VNA of this conventional type.
    (1) Advantest R3765CG
    (2) Anritsu MS4624D

    These conventional 4-Ports-VNA evaluate differential mode S-parameters by Software-Balun which is valid and useful for linear DUT.

    On the other hand, Advantest R3860A can do calibrated control of SG1 and SG2 regarding their amplitude and phase.

    (1) Set amplitude of SG1 and SG2 same accurately.
    (2) Set phase difference of SG1 and SG2 180degree accurately.

    These are done as automatic calibration process.

    So we can measure true large signal differential mode S-parameters by Advantest R3860A.

    Quote Originally Posted by FvM View Post
    If you only need the input related network parameters of the fully differential amplifier,
    most VNA should be able to doe the same measurement.
    Such method is valid only for linear DUT.
    http://www.designers-guide.org/Forum...m=1205240723#9
    Last edited by pancho_hideboo; 1st April 2017 at 11:30.



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    Re: True Large Signal Differential Input Impedance Evaluation




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    Re: True Large Signal Differential Input Impedance Evaluation

    See page-2 of the following.
    http://www.tek.com/sites/tek.com/fil...0W611320_0.pdf

    Tektronix TTR500 Series Vector Network Analyzer(VNA) have two RF signal sources.

    Do you think whether it can drive port1 and port2 out of phase by 180 degree at same time ?



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    Re: True Large Signal Differential Input Impedance Evaluation

    https://www.rohde-schwarz.com/produc...3493-9660.html

    We can do true differential measurement with this VNA.



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    Re: True Large Signal Differential Input Impedance Evaluation

    The following VNAs all supports true large signal differential measurement.

    Anritsu MS4640B

    Keysight 5242A PNA-X

    Rohde & Schwarz ZVA



    •   Alt24th June 2017, 06:26

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    Re: True Large Signal Differential Input Impedance Evaluation

    For True Large Signal Differential Input Impedance Evaluation, we must use the true differential mode and the VNA must support true differential mode, that is to say, every port of VNA must have its own VSG and VSA.

    http://www.av.it.pt/Medidas/Data/Man...ntial_Mode.htm

    http://www.keysight.com/upload/cmc_u...ueDiff_FAQ.pdf

    https://www.electrorent.com/forms/pd...asurements.pdf

    www.npl.co.uk/upload/pdf/090514_mmwug_barnett.pdf

    http://literature.cdn.keysight.com/l...989-4518EN.pdf

    http://www.microwavejournal.com/arti...va-and-r-s-zvt



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    Re: True Large Signal Differential Input Impedance Evaluation

    Refer to the book of HANDBOOK OF MICROWAVE COMPONENT MEASUREMENTS WITH ADVANCED VNA TECHNIQUES


    8.6 Distortion Measurements of Differential Devices 539
    8.6.1 Comparing Single Ended IMD Measurement to True Mode Measurements



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