On Fr, 8.07.2005, 21:33, John Steenbergen wrote:
> Stefan,
Hello John!
> I tried to use the equations:
> K = Rollet(S)
> Gmax = abs(S[2,1]/S[1,2])*(Ksqrt((K^2)1))
>
> Also reference eq. 1.146 in the technical documents.
>
> To calculate the max gain circles, but the result was way off the smith
> chart.
>
> Any ideas?
I am sorry that I did not respond for such a long time. But now I had
again a look at my mailinbox...
I assume the mails were about your 'NE85634107.S2P' file. If you look
at the Rollet (K) factor you see that it is uncondiionally stable at about
1GHZ (K > 1 and det(S) < 1). That is why the the gain circles are off
the smith chart. They are inside the smith chart if the twoport is
unconditionally stable and the given gain is less or equal than the
maximum gain.
If you compute the maximum gain at a stable point and then compute the
gain circle the radius is near zero. So
GaCircle (S)
with no gain given, looking for the maximum gain and computing the
gain circle makes no sense, because it computes a point, not a circle.
Now I wonder what all this is about? Please send an example what you
have done, where the problem is and what you wanted to simulate and
what you expect to see.
>> According to my notes the max gain is:
>>
>> Gmax = mag or abs (S21/S12) * (K  (K^21)^(1/2)
>>
>> Where K is the stability factor.
>>
>> Hope that is a help.
>>
>> John
>>
>>
>> On 7/8/05, Stefan Jahn <stefan@...> wrote:
>> >
>> > On Fr, 8.07.2005, 08:09, Michael.Margraf@... sagte:
>> >
>> > > Hello,
>> >
>> > Hi!
>> >
>> > >>> The last program (SuperStar) I used plotted the maximum gain at
>> the
>> > >>> calculated frequency so that was never a parameter. That clears a
>> > lot
>> > >>> up.
>> > >>
>> > >> Hm, that may be an option... Possibly we can do that as well.
>> > >> Michael: What do you think about it?
>> > >
>> > > The gain needs to be a parameter! Not only the maximum gain is
>> > > important. But perhaps the maximum gain can be the default
>> > > value if none is specified ?
>> >
>> > That's what I meant. Using the maximum availale gain if no specific
>> gain
>> >
>> > is given.
Cheers, Stefan.
