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Ken Kundert Global Moderator Offline Posts: 2384 Silicon Valley	Re: Printing frequency in AC output Reply #15 - Aug 30^th, 2006, 11:27am Agreed. Cadence should reinitialize every local variable to 0 before each non-transient step. That way, even if the models are re-evaluated at every step, they would behave exactly the same. -Ken
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jbdavid Community Fellow Offline Posts: 378 Silicon Valley	Re: Printing frequency in AC output Reply #16 - Aug 30^th, 2006, 10:58pm What would prevent a person from doing a parameter sweep with just a DCop and SinglePoint AC, where the AC frequency was a little different at each step.. BTW I want a simulator where I can do run 20ns AC(tb.dut.in_p,tp.dut.in_n) sweep Freq from 10K to 100G log 20 run 30ns
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Marq Kole

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Re: Printing frequency in AC output
Reply #17 - Aug 31^st, 2006, 12:08am

Geoffrey_Coram wrote on Aug 29^th, 2006, 8:32am:

Ken Kundert wrote on Aug 28^th, 2006, 8:49am:

3. It is not very useful; there are very few models that are both easy to describe in the frequency domain and hard to describe in the time domain.

I can howeer see Marq's point that, for an "instrumentation module" ie one that prints out information about the circuit, it is nice to be able to print the frequency value. I could imagine providing a %code to give the frequency.

I've been giving this some thought: with respect to the model safety aspects and limited to small-signal frequency domain, I can only see two extensions:

display format codes that allow one to output AC values of signals - but you might want additional formatters for getting polar representation, or only real part, imaginary part, phase or magnitude,
built-in S-parameter and Y-parameter models, along the lines of the Spice primitives mentioned in Annex E, using either a file or array just like the $table_model.

I really like these instrumentation modules because they allow me to compare the results in various simulators. Think of compact model development or IP library development.

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Marq Kole

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Re: Printing frequency in AC output
Reply #18 - Aug 31^st, 2006, 1:21am

One thing I forgot in the above list (but in a wat already mentioned by Geoffrey):

a display code to get the frequency, along the same line as the %M code for a hierachical name - without an actual argument, but with support for formatting codes similar to those for real numbers.

An additional option could be to have similar display output, but then during the small-signal noise analysis: again purely for instrumentation purposes.

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Ken Kundert

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Re: Printing frequency in AC output
Reply #19 - Aug 31^st, 2006, 9:22am

Marq,
I don't believe that an AHDL like Verilog-A or Verilog-AMS is the right language for this kind of post analysis analysis (or instrumentation modules as you call them). They are not a good fit. As you have already noticed, you would need to add complex arithmetic to the language, but that is just the beginning of the changes that would be needed. It completely changes the character of the language.

I spent a lot of time on this issue while I was at Cadence and developed the idea of having a measurement description language (or MDL) as a natural complement to the HDLs. Cadence eventually released SpectreMDL, but it is a very limited and primitive version of what was originally envisioned. As Jonathan proposed elsewhere in this Forum, it would be helpful to have a standardized MDL. I've often wondered if there would be any interest in developing and implementing such a standard. I believe it would be incredibly useful, but it would also be a lot of work.

-Ken

P. S. for Jonathan,
Spectre can do what you want. I give an example in section 3.4.4 (pg. 113) in my Spice and Spectre book.

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John O Donovan

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Re: Printing frequency in AC output
Reply #20 - Aug 31^st, 2006, 10:07am

Hi,

If you want to run a transient analysis to 30ns and use the oppoint at 20ns to run an AC type (ac, noise, sp, xf) analysis you can also use the 'actimes' and 'acnames' transient analysis parameters, i.e.

ac1 ac param=freq start=10K stop=100G log=20
tran1 tran stop=30ns actimes=[20ns] acnames=[ac1]

'actimes' and 'acnames' are vectors so you can run multiple analyses at multiple times during the tran.

Regards,
John

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jbdavid Community Fellow Offline Posts: 378 Silicon Valley	Re: Printing frequency in AC output Reply #21 - Sep 1^st, 2006, 11:25pm That would be the Spectre way of doing It.. I was thinking more of NCsim-AMS
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