[SOLVED] How to plot constant Q curves on the ADS datadisplay smith chart

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tahmis91

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Dear all,

Do anybody know how to plot the constant Q curves on the ADS keysight datadisplay? (I want to use them for matching) (I found that on the Smith chart utility tool, there is an option to play them, but I want to plot them on the data display, I mean, when I simulate "real-non ideal from a given technology design kit"

Thank you,
 

pancho_hideboo said:
Do you mean locuses of Q=X/R or Q=B/G on smith chart ?
Click to expand...

Yes, I mean locuses of Q = X/R ( Q isn't the same value for both X/R for circuit in serie or B/G for circuit in parallel ?! and, isnt the same for both Z chart or Y chart or ZY chart?)

Thank you,
 

pancho_hideboo said:
No.

Gamma=(Z/Z0-1)/(Z/Z0+1)=-(Y/Y0-1)/(Y/Y0+1)
Click to expand...

Yes, of course there is a shift of 180 degree between Gamma calaculated according to Z and that calculated with Y, I didn't say the opposite.

But, the locus of constante Q in the Z, Y, and ZY chat is the same, for example, for Q=1, the locus ploted in the Z, Y and ZY chart is the same.

Anyways, how to plot the constant Q circle in the Z chart

Thanks,
 

Draw partial circle based on definition.
Center is (0, +1/Q) or (0, -1/Q).
Radius is sqrt(1+1/Q^2).
 
Last edited:

pancho_hideboo said:
Draw partial circle based on definition.
Center is (0, +1/Q) or (0, -1/Q).
Radius is sqrt(1+1/Q^2).
Click to expand...

I don't know how to access to the resistance and reactance of the smith chart on the ADS datadisplay to plot the Q
And, I don't know how to plot the equation of a circle on ADS datadisplay

I want to notice that is not as simple as we could think, I searched but didnt find, this is why I am asking here

Thanks
 

volker@muehlhaus said:
I'm also interested.
Please tell us about the simple method how to draw these circles in ADS data display.
Click to expand...
If needed, create custom AEL function.

Actually I have custom Skill function "Constat_Q_Circle(Q)" which returns Gamma for Q in Cadence dfII.

tahmis91 said:
There is one solution on the attached document,
Click to expand...
It's too unefficient since S is bilnear transformation of z, S=(z-1)/(z+1).

tahmis91 said:
I found that on the Smith chart utility tool, there is an option to play them
Click to expand...
I think a following is good than Smith chart utility tool of ADS.

https://www.fritz.dellsperger.net/smith.html
 

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pancho_hideboo said:
Do you mean locuses of Q=X/R or Q=B/G on smith chart ?
Click to expand...

Qserie=X/R=Qparallel=B/G => So, it results on the same

It is simple to demonstrate by taking a serie R-L circuit and calulate the parallel equivalent R-L...
 

"Constant_Q_Circle.ael"
Code: 
defun Constant_Q_Circle(Q)
{
  decl radius, S0p, th1, th2, dth, thp, nlen, Sp, Sm, Sq;

  radius = sqrt( 1 + 1/(Q*Q) );
  S0p = -j * (1/Q);

  th1 = acos(1 / radius);
  th2 = pi - th1;
  dth = (th2 - th1) / 50;

  thp = [th1::dth::th2];
  nlen = sweep_size(thp);
  
  Sp = S0p + radius * exp(j*thp);
  Sp[0] = 1.0;
  Sp[nlen-1] = -1.0;
  
  Sm = conj(Sp);

  Sq = [ Sp, Sm[nlen-2::-1::0] ];

  return Sq;
}
 

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