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}

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

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

Yes, 10dBm at most.

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 ?

The Advantest obviously does what you explicitly excluded in post #1, calculating the differential impedance from a two port measurement.
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.



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?

Wrong.

Correct.

Again see block diagram of https://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.

Such method is valid only for linear DUT.
http://www.designers-guide.org/Forum...m=1205240723#9

See page-4 of https://www.rohde-schwarz.com/file/R...3768_R3770.pdf

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 ?

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

We can do true differential measurement with this VNA.

The following VNAs all supports true large signal differential measurement.

Anritsu MS4640B

Keysight 5242A PNA-X

Rohde & Schwarz ZVA

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

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