What are the switch terms?
Michael Wollensack METAS
- What are the switch terms?
- Which standard (Thru, Match or High Reflect) should I measure?
- Is it necessary to have those switch terms for my R&S VNA?
Michael Wollensack METAS
- The switch terms describe the imperfect load when the source is switch to the other port.
- A thru connection or an adapter with low insertion loss.
- The switch terms are necessary for all VNA with more than one port.
Ondřej Morávek
Michael Wollensack METAS
tbu...@maurymw.com
You said that the switch terms must be a thru connection or an adapter with low insertion loss. However, when I look in the example folder of VNA tools II called "01_Basic_Example_N(f-m)" and display the S parameters of the so called "Switchterms_01.sdatb" file in the data explorer, S21 and S12 magnitude are both extremely small indicating no transmission between ports 1 and 2. Why is that?
Michael Wollensack METAS
Tasnim Khanam
Michael Wollensack METAS
Dao Pham
Hi,
I have a question about the switch-term corrected S-parameters for the 4-port VNA measurement.
In fact, with the 2-port VNA model, we can measure 2 switch terms (in forward and reverse directions) then apply the switch-term correction as following:
In other way, we can apply the switch terms to the measured S-matrix (Sm) under the matrix manipulation as below:
For the switch-term correction on a 4-port VNA system, I’m thinking about applying the same matrix manipulation as the 2-port VNA case
But the problem is that I haven’t found down the references/publications to prove this approach.
I would be grateful if any experts here could give me some ideas or references regarding to taking all switch-terms into account for the S-parameter measurements with 4-port VNA.
Thank you in advance for your help.
Best Regards,
Dao PHAM
Michael Wollensack METAS
/// <summary>
/// Remove Switch Terms from N-Port
/// </summary>
/// <typeparam name="T">Real Number Type</typeparam>
/// <param name="a">N-Port S-Parameter Data</param>
/// <param name="swt">Switch Terms</param>
/// <returns>N-Port S-Parameter Data</returns>
public static SParamData<T> RemoveSwitchTerms<T>(SParamData<T> a, SParamData<T> swt)
where T : IRealNumber<T>, new ()
{
int nports = a.NPorts;
int nfreq = a.NFreq;
if (nports != swt.NPorts) throw new System.Exception("Number of ports must agree");
if (nfreq != swt.NFreq) throw new System.Exception("Number of frequency points must agree");
SParamData<T> swt2 = ChangeZr(swt, a.PortZr);
SParamData<T> b = new SParamData<T>(a.Frequency, a.Ports, a.PortZr);
Parallel.For(0, nfreq, (int i0) =>
//for (int i0 = 0; i0 < nfreq; i0++)
{
Complex<T>[][] temp = new Complex<T>[nports][];
for (int i1 = 0; i1 < nports; i1++)
{
temp[i1] = new Complex<T>[nports];
for (int i2 = 0; i2 < nports; i2++)
{
if (i1 == i2)
temp[i1][i2] = 1;
else
temp[i1][i2] = a[i0, i1, i2] * swt2[i0, i1, i1];
}
}
//b[i0] = LinAlg.Dot(a[i0], LinAlg.Inv(temp));
b[i0] = LinAlg.Dot_A_invB(a[i0], temp);
});
return b;
}
Dao Pham
Mertcan ASLAN
Michael Wollensack METAS
Hi,
with a HP8753D you cannot measure the switch terms, because it has only 3 receivers and not 4.
Therefor you can only perform only SOLT calibrations and not Unknown Thru for example.
Regards
Michael
Mertcan ASLAN
Juerg Ruefenacht
Hi Mert,
This is are
very good reason to attend our VNA Tools training course including the
additional free VNA Expert Day (see: METAS courses ).
Unfortunately,
our workload doesn't allow us to go into more detail, especially since VNA
Tools is available for free. But there are many textbooks available, or check
out the free resources on the internet.
Our goal is to keep the VNA Tools as a free
software and better visibility with a larger number of course registrations help
us to get support from our management to allocate the necessary resources. Therefore,
your support will help us that we can further develop and improve our free VNA
metrology application VNA Tools.
Thanks,
Juerg