How to match a circuit to non-50ohm system?

[rhjang]

I can match a circuit to 50ohm, but how to match a circuit to non-50ohm system with 50ohm terminated network analyzer? :?:

 

[happy_99]

I can match a circuit to 50ohm, but how to match a circuit to non-50ohm system with 50ohm terminated network analyzer? :?:

Could you pls provide the details to match as circuit to 50 ohms.

Thank You

happy_99

 

[flatulent]

You can make minimum loss resistive pads. You then have to calibrate the analyzer with the pads in and with opens, shorts, and the not-50 ohm loads on the far end of the pads.

 

[activewei]

You can use transformer if the impedance is as high as 1K Ohms.
Alternative: Agilent Technologies has a Network Analyzer that can measure impedance besides 50 Ohm. But the equipment is not cheap....

 

[caocao]

Hi
I think you can use a very original method,such as 50~150~50ohm ,the you can use you NA to conclude the performance of non -50ohm system .

 

[flyhigh]

You can use transformer if the impedance is as high as 1K Ohms.
Alternative: @gilent Technologies has a Network Analyzer that can measure impedance besides 50 Ohm. But the equipment is not cheap....

Hi,

yes @gilent has some nice VNA pieces in its gamut of instruments. They are most recent generation and tipically can measure the differential/common mode S parameters. However, the normalizing impedance option is not the reason for the high price. It is a very simple math on measured Spars to normalize them to impedance different from 50Ohm and show it on a display. With a little programming skills it will not be a problem to acomplish this with a PC and GP-IB card. This can be finished in a day, equations for the normalization are widely available in the literature.

flyhigh

 

[883]

for general use , such as 75ohm. 1Mohm , and 110ohm , the Aglient provide a standard impedance converter,
other else , you must setup a match network base on you using aera

 

[zfl]

Yes,the lambada/4 transform is a very good choice,if the impedance is suitable!

 

[iambbcat]

Maybe a SmithChart can solve some problem

 

[eecly]

Hi,

You can perform a conjugate match


eecly

 

[activewei]

to flyhigh: Do you have the literature on the method explained? I am interested to know more.....

 

[flyhigh]

Hi,

no, I don't have anything on paper or in electronic form. I attended @gilent workshop and they were talking about these options built in the instruments. They were targeting the use of PNA series network analyzers and one of the novelity was the measurement flow with the PNAs. It has a point where user can input terminal impedance. It is especially needed for accomodating differential/common mode measurements.

Considering math dealing with renormalisation of S pars to differnet impedance, I think the relations from the famous books by Pozar or Colin can work as well. They are primarily inteded to handle S parameters for the case the termination lines impedances are different.


T sqrt(Zoj)
Sij= Sij _________
sqrt(Zoi)


(sorry, I don't know any clever way to input this formula it keeps comming out massy, hopefully you might get an idea what I have in mind)

So, if you have older NA, I think you can input your S pars to a PC via GP-IB, renormalize them and then send back to NA to view your matching/tuning on its display almost in real time.

Hope this will help solve your problem.

flyhigh

 

[IICCEE]

just similar to the 50 ohm system.
only to turn the s parameter to the special termind.

You may refer the guptar's book on microwave CAD.

In this case the S parameter is call generlized S parameter.

 

[IICCEE]

And in the CAD tool suits,you also may definite the port reference impedance.

 

[activewei]

A good article found on this topic...

Introduction
S-parameters are dependent on the impedance to which they are referenced and many measurements are now performed in a
non-50 ohm world. Matching and other tasks are now often referenced to something other than 50 ohms but calibrations in the
native unusual impedance may be difficult or untraceable. Arbitrary impedance transformations allow measurements to be
presented as if performed in the desired impedance......

 

[mgf]

to: eecly -

how do you do a conjugate match? have u any documentation on this issue /

mgf

 

[v4eda]

I can match a circuit to 50ohm, but how to match a circuit to non-50ohm system with 50ohm terminated network analyzer? :?:

It's very simple - since you are able to match the circuit to a 50 ohm system fo matching to any other reference impedance just use an impedance transformer - a lambda/4 line of impedance = sqrt (Zo(=50) * Zonew(other impedance)); this thing works for higher frequencies as the length of the transmission line would be larger at lower frequencies.
Another way is to denormalise the load impedance by multiplying it by 50 and dividing it by the other reference impedance and plot it in a normalised smith chart.

 

[myicejade]

you can match any impedance by ADS tool or other ,like microwave office and so on

 

[jyfx]

he lambada/4 transform is a very good choice,if the impedance is suitable!
some litter tools can help u?

 

[mhtplsh]

Another way is to denormalise the load impedance by multiplying it by 50 and dividing it by the other reference impedance and plot it in a normalised smith chart.

This means if i want to design for 75 ohm input output, i hv to just devide input output load impedance by 1.5. then use it for matching purpose in smithchart.
Is this ok?