Agilent ADS problem: mu() factor for stability
I have a schematics file with two different amplifier circuits. Circuit A uses Port 1 and Port 2, circuit B uses Port 3 and Port 4. I'd like to simulate stability for both of them simultaneously, to be able to compare them both.
To simulate stability when there is only one circuit which uses Port 1 and Port 2 (as in the following picture), I use the measurement equation
Mu1=mu(S)
If I now put in a second circuit into the schematic file (to see what I mean see next picture), which naturally is between port numbers 3 and 4 and start simulating, I get an error message:
Evaluation failed for 'Mu1=mu(S)': "Mu1": (Unknown message)
How can I tell ADS it should calculate the μ-factor for circuit A AND circuit B?
(as an alternative, I tried it with the following equations - the results are different to mu() though and don"t match to the stability circles, so they don't help me:
DeltaMag1=mag(S(1,1)*S(2,2)-S(1,2)*S(2,1)) mu_1 = (1-mag(S22)*mag(S22)) / ( mag(S11-conj(S22)*DeltaMag1) + mag(S12*S21) )
any help appreciated,
arefeidi
Maybe my explanation was a bit confusing, hopefully another picture will make my problem more clear. Within one schematics-file I have two circuits. And I'd like to compare the μ-stability-factor for both of them:
Though when I start simulating, I get the following error message (ADS seems to be confused by Term3 and Term4):
How can I tell ADS that it should calculate the μ-factor for BOTH of the circuits within one simulation?
Added after 10 minutes:
I already tried to enter the equations for the μ-factor directly, which I found in the ADS help and in Pozar's book "Microwave Engineering":
This way I can calculate μ for both circuits simultaneously - but the results are wrong!
The results are different to the ADS mu(S) and mu_prime(S) functions:
As known, μ should give the distance between the Smith-chart center and the unstable region:
- when I compare the ADS mu(S) to the stability circles, this is true: μ = distance between smith center and unstable region
- the results of the equations I entered myself are wrong though, in this case μ does not equal the distance between smith center and unstable region
So what can I do to calculate μ simultaneously (and correctly) for two (or more) circuits?
Any help appreciated,
arefeidi
why not simulate separately and display two graphs in single data display?
Completely forgot this topic, sorry...
Thanks, this is also how I've done it then. Stupid me, when I first asked I didn't know it was possible to display separately simulated results in a common data display window
Anyway, I still wonder why the ADS Mu() and MuPrime() functions yield to different results compared to the formulas given in Pozar and the ADS help itself:
you are comparing mu and mu_prime.
Mu_prime have S22 in numerator
where as
mu will have S11
Ouch, copy & paste...I added the old picture - here's one showing all diagrams:
You can also see the differences here - the calculated results using the formula are definitely wrong. Mu_formula goes below 1 again above 5 GHz, but MuPrime_formula doesn"t - this can't happen in reality. Stability circle analysis shows both calculated values are wrong - Mu() and MuPrime() are correct though.
I don't know what I could be making wrong here using the formulas as shown in the picture