time domain vswr

[faheem1234@hotmail.com]

Hi there,

I have written a program for Narrow band (8.5 GHz to 10.5 GHz) and Broad band (40 MHz to 20 GHz).

Program works fine but just left with one issue.

In program I want to do “Time Domain VSWR” measurement for Broad band frequency for input port S(1,1). I have S-Parameters (ARRAY OF 100 NUMERIC NUMBERS)  of that port but I don’t know the mathematical equation to convert all Frequency domain S-parameters into TD.

I have tried some function after watching some videos on youtube but i am not convinced from output response.

Is there any link or can you help me out with it.

If anyone happy to help me, I can attach my .VI here

Thanks

Faheem

[MariusU]

Hi Faheem,

To clarify, are you refering to Voltage Standing Wave Ratio? 

By stating that you wrote a program for Narrow Band and Broad Band do you mean that you wrote a vi which sweeps through the frequencies you specified?

It does seems like you are talking about models that you made or am trying to use. I think to better understand the problem I would need to see the code to advise further.

To be honest I am not too familiar of what you are trying to do but I do have a decent background in control theory, which seems to be what you are after so I would like to give it a go after I see your vi.

Kind Regards,

[faheem1234@hotmail.com]

HI THERE,

I have attached my VI please have a look and I have written 3 notes and you will see them on program.

1st I am calling for Narrow band and then Broadband.

and Yes, i am talking about voltage standing wave ratio

Regards,

Faheem

[MariusU]

Hi,

It looks like there is quite a lot going on in your code and I am not quite sure what is the results you are getting.

I think to resolve your issue you need to clearly define what you are getting in terms of output. Is it even possible to even convert it? Or do you even have to perform similar calculations but for the time domain?

Usually you go from the frequency domain to time domain via inverse laplace transform, however I am not sure if you are actually getting a laplace equation or is it just some frequency measurements.

Kind Regards,

[faheem1234@hotmail.com]

Hi there,

Thanks for your reply

Let me show you respose of BroadBand I have from VNA

FREQUENCY    S11 MAGNITUDE          S11 PHASE              S21 M                       S21 P                     S12M                       S12P                       S22M                          S22P

9.000000000      1.353432E-01                142.260             3.142483E-01             -71.874             3.069935E-01             -71.256            5.076511E-02                 -163.088
9.040000000      1.386814E-01                110.749             3.052184E-01            -109.157             3.159364E-01             -109.973            2.928660E-02             -162.441
9.080000000      1.239026E-01                82.113               3.110454E-01            -146.900             3.064758E-01             -145.673             2.352772E-02             -138.830
9.120000000      9.884222E-02                57.014               3.091927E-01             177.517             3.157930E-01             175.915             5.040505E-02              -127.002
9.160000000      7.625741E-02                36.134               2.981620E-01             138.250             3.059292E-01             139.311             7.309607E-02               -136.837

) NOW BY USING LABVIEW PROGRAM, I WANT TO CONVERT THIS INTO TIME DOMAIN format.  Is it clear now or am I still missing some information?

Regards

Faheem

[jamiva]

You can’t convert the s-parameters into a time domain VSWR. However, you can calculate the VSWR from the S11 data for each measured frequency point. VSWR = (1+|gamma|) / (1-|gamma|). At 9 GHz it would be (if I got my units correct):

VSWR = (1 + 0.1353432) / (1 – 0.1353432) = 1.313

A “Time Domain VSWR” is a complexly different test method. Your VNA may support that type of testing. Google “Time Domain VSWR” and click on the link to the Agilent AppNote. It is a very good resource on how to perform that test.