[50 pts for help] SpectreRF problem

spectrerf manual

Hi members,

I'm facing problems in simulating a PLL phase noise using SpectreRF. Actually, I'm performing pss simulation I fill the SpectreRF pss window but when I start the simulation I got a report of errors saying that V1 is inconsistant with autonomous circuits.
It says that V1 is a vpulse and that's the cause of the error. Actually I needed and I used it to generate the input reference clock for the PLL. In fact the transiant simulation was successfull with the same circuit. I dont know what's the problem with the pss case.

I attached the circuits that I am simulating as well as the error mentionned.

Please help.

Many thanks.

spectrerf periodic analysis

autonomous circuit means that a one doesn't have any time-varying input sources. Your circuit is driven. You have to turn off the oscillator button in the PSS analysis.

spectrerf vco tutorial

Hi yxo and Hi all,

I still dont have solved this problem. I need your help to perform a pss simulation for the PLL. I readed a wonderful tutorial on SpectreRF (VCO workshop from Cadence) that you can download from here:

#1117931

My problem is that, every time I start a simulation I get an error due to the fact that the PLL is using a pulse generator for synchronization. It seems that SpectreRF dont accept periodic generators.
The periodic clock signal is mendatory in order to simulate the PLL.

So how can I simulate my PLL


I'll donate 50 pts for real helper (with many thanks of course )

pss spectrerf

AdvaRes said:

Hi yxo and Hi all,

I still dont have solved this problem.
... So how can I simulate my PLL
I'll donate 50 pts for real helper (with many thanks of course )

Click to expand...

Hi again AdvaRes,
did you solve it in the meantime? I found this discussion:

... and another Cadence workshop tutorial, which might be helpful.
Cheers, erikl

tutorial spectrerf

Hi Erikl,
Thanks for your reply. Unfortunately I didn't progress .

In the refered thread it is said that pss can't run with a periodic source and the solution is to use a sine wave VerilogA instead. So the question is can we simulate spice and VeriogA together using SpectreRF ?

spectrerf pss analysis

AdvaRes said:

In the refered thread it is said that pss can't run with a periodic source and the solution is to use a sine wave VerilogA instead.

Click to expand...

Hi AdvaRes,
I think pss can also be run with a periodic source, if you follow yxo's advice (s. above). This seems to be confirmed - the other way round for an autonomous circuit - on page 7 of the VCO workshop tutorial which I sent you yesterday.

AdvaRes said:

So the question is can we simulate spice and VeriogA together using SpectreRF ?

Click to expand...

Sure: Just study $CDS_INST_DIR/doc/spectreRF/spectreRF.pdf
It contains also a lot of stuff on VCO resp. PLL simulation.
Cheers, erikl

site:www.edaboard.com qpss analysis

erikl said:

AdvaRes said:

In the refered thread it is said that pss can't run with a periodic source and the solution is to use a sine wave VerilogA instead.

Click to expand...

Hi AdvaRes,
I think pss can also be run with a periodic source, if you follow yxo's advice (s. above). This seems to be confirmed - the other way round for an autonomous circuit - on page 7 of the VCO workshop tutorial which I sent you yesterday.

AdvaRes said:

So the question is can we simulate spice and VeriogA together using SpectreRF ?

Click to expand...

Sure: Just study $CDS_INST_DIR/doc/spectreRF/spectreRF.pdf
It contains also a lot of stuff on VCO resp. PLL simulation.
Cheers, erikl

Click to expand...

I'll investigates these points immediatly. I'll be back asap !
Thanks Elrikl !
Thank you all.

multiple clock qpss

Hi,
In fact, both autonomous and driven(non-autonomous) circuits can be successfully simulated with PSS but you need to be aware of how to configure the simulation. I quote following from the spectreRF manual. Just a moment ago, I have simulated a SC circuit with PSS, QPSS (with periodic clock signal and sinsoid input). All you need to do is simply "do not supply the pair of nodes in PSS".

=====================================================

The PSS analysis works with both autonomous and driven circuits.

*Autonomous (non-driven) circuits are time-invariant circuits with time-varying responses. Thus, autonomous circuits generate non-constant waveforms even though they are not driven by a time-varying stimulus.The most common autonomous circuit is an oscillator.

*Driven (non-autonomous) circuits require some time-varying stimulus to generate a time-varying response. Some common driven circuits include amplifiers, filters, mixers, and so on.

For autonomous circuits, since they do not have drive signals and you do not know the actual period of oscillation in advance, you estimate the oscillation period and the PSS analysis computes the precise period along with the periodic solution waveforms. PSS analysis of an autonomous circuit, requires you to specify a pair of nodes, p and n. In fact this is how PSS analysis determines whether it is being applied to an autonomous or a driven circuit. If the pair of nodes is supplied, the PSS analysis assumes the circuit is autonomous; if not, the circuit is assumed to be driven. See Chapter 5, "Simulating Oscillators," for an example.

For driven circuits, you specify either the period of the analysis, the period parameter, or its corresponding fundamental frequency, the fund parameter. The period parameter value must be an integer multiple of the period of the drive signals.

The errpreset parameter works differently for autonomous (non-driven) and driven (non-autonomous) circuits. For detailed information, see "The errpreset Parameter in PSS Analysis".

spectre rf manul

i am not too familiar with these analyses, but have you tried qpss or envlp analysis? i think they support multitone circuits. i think aglient HB solver would be more appropriate overall from what i've read about it.