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Simulators >> RF Simulators >> Transmission-line oscillator: problem with PSS
https://designers-guide.org/forum/YaBB.pl?num=1258711290

Message started by DoYouLinux on Nov 20^th, 2009, 2:01am

Title: Transmission-line oscillator: problem with PSS
Post by DoYouLinux on Nov 20^th, 2009, 2:01am

Hi all,

I am trying to simulate an oscillator with PSS. In this oscillator, two transmission lines are used to implement the tank. The model of the transmission line was extracted from HFSS as RLGC model.

When I simulated, PSS failed, and it mentioned that it cannot support directly to distributed components. It also suggested me to use Harmonic balance method.

As I see from PSS, I have "Shooting" and "Flexible balance",

So, is it correct that I should choose "Flexible balance" ?? :-?

I tried to use it, PSS failed again. Perhaps I do not know how to set the paramters in Flexible balance correctly.

If anyone used Flexible balance mode in PSS before, please suggest me how to simulate my oscillator in this mode.

Thank you in advance :)

DYL

Title: Re: Transmission-line oscillator: problem with PSS
Post by pancho_hideboo on Nov 20^th, 2009, 3:18am

DoYouLinux wrote on Nov 20^th, 2009, 2:01am:

I am trying to simulate an oscillator with PSS.

What EDA Tool do you use ?
There are many simulators which have an analysis called as "PSS".

DoYouLinux wrote on Nov 20^th, 2009, 2:01am:

In this oscillator, two transmission lines are used to implement the tank.
The model of the transmission line was extracted from HFSS as RLGC model.

Is it truely "RLGC" model ?

DoYouLinux wrote on Nov 20^th, 2009, 2:01am:

When I simulated, PSS failed, and it mentioned that it cannot support directly to distributed components.
It also suggested me to use Harmonic balance method.
As I see from PSS, I have "Shooting" and "Flexible balance",
So, is it correct that I should choose "Flexible balance" ?? :-?

If you mean PSS of Cadence Spectre, "Flexible balance" is "Harmonic balance".
I think Cadence did not like to use word of "Harmonic balance" obstinately due to historical reason.

Currently Cadence call it "Harmonic balance".

DoYouLinux wrote on Nov 20^th, 2009, 2:01am:

I tried to use it, PSS failed again.
Perhaps I do not know how to set the paramters in Flexible balance correctly.
If anyone used Flexible balance mode in PSS before,
please suggest me how to simulate my oscillator in this mode.

http://www.designers-guide.org/Forum/YaBB.pl?num=1228240587
http://www.designers-guide.org/Forum/YaBB.pl?num=1205223090
http://www.designers-guide.org/Forum/YaBB.pl?num=1237187544

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Title: Re: Transmission-line oscillator: problem with PSS
Post by Andrew Beckett on Nov 24^th, 2009, 10:05am

DoYouLinux,

I'll post a more friendly (and hopefully helpful) post. Perhaps you can answer some questions:

1. What version of spectre are you using? (I know you're using spectre, from the terminology you use). In the simulator output log file, it should tell you the subversion.
2. How are you instantiating the RLGC model? Is this being done using the RLGC matrices parameters for an "mtline" component? Or is it a lumped equivalent model?
3. If you are using an older version of spectreRF, you may want to specify the tstab as 0 to prevent it needing to simulate with a "transient assist" phase - this is often the problematic part when using a frequency domain model (if that's what you have) as it needs to work backwards from the frequency domain model, and that can be tricky (although it is much more robust in recent MMSIM versions). Nowadays, when using harmonic balance (aka "flexible balance") within spectre, tstab=0 by default, so that it doesn't do transient assist unless you ask for it.

I may be able to provide more suggestions once I've had some answers to the above.

Best Regards,

Andrew.