Designer’s Guide Community

supermoment

Senior Member

Offline

Posts: 167

pss convergent issue in osc phase model.
Aug 08^th, 2010, 3:13am

I simulated the osc phase model but fail to run pss & pnoise.

"Analysis `pss' terminated prematurely due to error."
It is due to convergent issue in pss run.

The input node is connected a voltage source vdc or idc with a ideal res.

Code:

`include "disciplines.vams"
	  discipline phase
		    potential Angle;
	  enddiscipline


`include "constants.vams"
`include "disciplines.vams"

module phasemodel_osc(in, out);

	  input  in;
	  output out;
	  phase  out;
	  voltage in;

	  parameter real gain = 1 from (0:inf);  //Transfer gain, Kvco (Hz/V)
	  parameter real n=0 from [0:inf);   //white output phase noise at 1Hz (rad^2/Hz)
	  parameter real fc=0 from [0:inf);  //flicker noise conrer freq (Hz)

	  analog begin
		    Theta(out) <+2*`M_PI*gain*idt(V(in));
		    Theta(out) <+ flicker_noise(n, 2, "wpn") + flicker_noise(n*fc, 3, "fpn");
	  end


endmodule

Back to top

IP Logged

supermoment Senior Member Offline Posts: 167	Re: pss convergent issue in osc phase model. Reply #1 - Aug 8^th, 2010, 6:06am I am a novice on RF analysis. I want to study the phase noise of each components in the whole PLL. I know CPPsim can make it easily. I just test out the osc alone. Since the input is a voltage, i set a voltage in the input. The reason to use pss is to observe the pnoise, which require pss run.
Back to top	IP Logged

pancho_hideboo

Senior Fellow

Offline

Posts: 1424
Real Homeless

Re: pss convergent issue in osc phase model.
Reply #2 - Aug 8^th, 2010, 6:43am

supermoment wrote on Aug 8^th, 2010, 6:06am:

The reason to use pss is to observe the pnoise, which require pss run.

You can't understand concept of "Phase Domain Model" at all.

supermoment wrote on Aug 8^th, 2010, 3:13am:

The input node is connected a voltage source vdc or idc with a ideal res.

Show me your netlist.

In your netlist, what is large signal ?
"Phase Domain Model" is not autonomous circuit.

Again see http://www.designers-guide.org/Forum/YaBB.pl?num=1280215169/7#7
Also see http://edocs.soco.agilent.com/display/ads2009/Phase+Noise+Simulations+using+Smal...

Here conventional small signal AC(Noise) Analyses are used.

Back to top

« Last Edit: Aug 8^th, 2010, 8:06am by pancho_hideboo »

Kita━━━━━━(ﾟ∀ﾟ)━━━━━━ !!!!!
http://www7.plala.or.jp/ungeromeppa/flash/kita.html
http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related

IP Logged

Ken Kundert

Global Moderator

Online

Posts: 2386
Silicon Valley

Re: pss convergent issue in osc phase model.
Reply #3 - Aug 8^th, 2010, 10:24am

You are simulating a phase-domain model of the oscillator alone? Not in a feedback loop? And you are doing it with PSS? That won't work. The phase-domain model of an oscillator is an integrator, which does not have a periodic solution.

You don't need PSS when you are simulating a phase-domain model, a simple noise analysis will do because the signals themselves are formulated in terms of phase, any noise you see on a phase signal with naturally be phase noise.

-Ken

Back to top

IP Logged

supermoment

Senior Member

Offline

Posts: 167

Re: pss convergent issue in osc phase model.
Reply #4 - Aug 8^th, 2010, 10:56pm

Thank you.

I eventually have made it by putting everything together. It could be analyzed in noise analysis and pnoise analysis (same result as in noise analysis)
The problem previously i got is that I did not have phase noise source :p

Again, thanks for your patience.

the next thing is to extract transistor level behavior from PSS & Pnoise run.

Back to top

IP Logged