How to plot Noise Modulating Function for VCOs in Cadence Virtuoso?

Hi Srayan,  

We don't have a specific "NMF" button in the Direct Plot form.  If you wanted that specifically, you'd need to file a Case on https://support.cadence.com so an Enhancement request CCR could be filed.

However...

In spectre standalone:  You can use the option separatenoise=yes in the pnoise (or hbnoise) line of the netlist.  It will give more info about the device noise sources and transfer functions.   

In ADE:  look in the "Spectre Circuit Simulator and Accelerated Parallel Simulator RF Analysis in ADE Explorer User Guide 21.1" and search for "Noise Separation".  It will talk about the implementation in ADE.

I hope that helps some!

best regards,

Tawna

Thank you.

I'll get back to you if necessary, I hope that's alright.

Dear Srayan,

Srayan said:

I would like to plot the NMF for ring oscillators as shown in Fig. 15 of the paper, "Hajimiri, Ali, and Thomas H. Lee. "A general theory of phase noise in electrical oscillators." IEEE journal of solid-state circuits 33.2 (1998)"

Can you suggest a suitable method for the same?

Please excuse my misunderstanding, but how is this question different from the question you posed in your initial Forum post :

Srayan said:

I would like to plot the the Noise Modulating Function (NMF) for the oscillating nodes in any VCO. What are the steps for the same?

If so, I can not add anything new to the methodology I proposed. Excuse my misunderstanding if I am not interpreting your latest question correctly.

Srayan said:

Furthermore, could you please confirm whether the modulation function m(t) described in the paper, "S. Galeone and M. P. Kennedy, "A comparison of simulation strategies for estimating phase noise in oscillators," 2017 13th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME), 2017, pp. 213-216" is the same thing as NMF (you can find m(t) on page 4 just below equation 9).

Yes, to my knowledge.

Srayan said:

If that's the case then have we been plotting the effective ISF as described in equation 9 of the same paper by saving the PPV data?

I mentioned earlier that the ISF and PPV differ - they are not the same . Please refer to Equation 6 of the second paper you are referencing. 

Shawn

ShawnLogan said:

Srayan said:

1. Aren't the PPV data plot and ISF plot the same thing? Or are they different but convey the same message (sensitivity of transient waveforms to charge injection)?

The two are slightly different in that an ISF plot (referred to as ) is computed as follows:

where To is the period of the steady-state solution, ∆q is the injected charge in a series of time-domain simulations, qmax is the maximum charge displacement between the nodes you are measuring the phase perturbation. As such, it is a unitless quantity.

A ppv plot of the same oscillator (referred to as  ) can be obtained by a similar set of simulations, but the phase change measured at each simulation is normalized to the injected charge. Therefore, it is not a unitless quantity. Hence, as you state, the two convey similar information, but are not identical.

Hi Srayan,

As I mentioned before, please contact Cadence Customer Support https://support.cadence.com and file a Case (essentially a "service request") for questions like this.  We will investigate with R&D and file any necessary enhancement CCRs (the method we use to make changes to our software).   You are welcome to add me to the cc list of the Case.

I work closely with both R&D and Customer Support - I can get this to the right person in R&D.

best regards,

Tawna

Hello,

You provided a method for plotting the NMF for colpitts oscillator, and your solution involved taking the PPV plots for the source node and the oscillating node. This time I am asking for a ring oscillator. I have the PPV plot for the oscillating node, but how do I plot the NMF?

Regarding the final query I made,"If that's the case then have we been plotting the effective ISF as described in equation 9 of the same paper by saving the PPV data?"

I am asking whether the plot obtained from the PPV data is comparable to ISF plot or the effective ISF(ISF*NMF) plot? I understand ISF and PPV plots are different but they look very similar. Am I making any mistake while plotting?

I have attached the ISF/PPV plots for square and sinusoidal waves. Are these plots the same as effective ISF?

Best Regards,

Srayan Sankar Chatterjee

Dear Srayan,

Srayan said:

You provided a method for plotting the NMF for colpitts oscillator, and your solution involved taking the PPV plots for the source node and the oscillating node. This time I am asking for a ring oscillator. I have the PPV plot for the oscillating node, but how do I plot the NMF?

The methodology is the same for a ring oscillator as it is a harmonic oscillator Srayan. If you plot the ppv for one of the other nodes of your ring oscillator, you will find that it looks almost the same as the ppv of the output node you show in blue. As clearly outlined in your reference, this is expected . The NMF for that interio node is derived from these two ppv.

Srayan said:

I am asking whether the plot obtained from the PPV data is comparable to ISF plot or the effective ISF(ISF*NMF) plot? I understand ISF and PPV plots are different but they look very similar. Am I making any mistake while plotting?

They do look similar since they are linearly related. However, the ppv is not unitless and has the units 1/A. If you look at the y-axes of the ppv plots you shown in yellow and blue, their units are (1/V). Further, for the ring oscillator, whose sensitivity to noise is far greater than the harmonic VCO, note its y-axis is 1e3* (1/V).

Srayan said:

I have attached the ISF/PPV plots for square and sinusoidal waves. Are these plots the same as effective ISF?

I think ti tried to just answer this question...I hope anyway!

Shawn

Hello,

I've plotted the PPV for a colpitts oscillator. The red one is of the drain node and yellow one is of the source. I even exported the data to an excel sheet and tried plotting after reflecting the plots about X-axis and changing the X-axis to radians. Even then the plots are not comparable to the ones found in literature or even the ones you had shared earlier. Any suggestions what I might be doing wrong? My setup oscillates around 5 GHz.

Best Regards,

Srayan Sankar Chatterjee

Srayan,

As Tawna has suggested more than once, please contact customer support. I believe you're at an academic institution but it should still be possible for a support case (service request) to be created by your institution via the My Cases menu at http://support.cadence.com 

As Tawna mentioned, she's been talking to R&D about this, and whilst we definitely appreciate Shawn's help on this, it makes most sense to have it dealt with by Cadence rather than users in the community.

I'd love to spend the time digging into this myself (I do work for Cadence), but unfortunately I don't have the bandwidth to do so at the moment - hence our suggestion to contact support about this. That's what it's for... you get to the product experts that way.

Thanks,

Andrew

Hello,

I will be doing that once I receive the host ID details required for filing a case from my institute. In the meantime any kind of help will be appreciated.

Best Regards,

Srayan Sankar Chatterjee

Hello,

I have tried filing a case at cadence support. I have also mailed universityprogram@cadence.com and support@cadence.com with my host ID and a form "Academic Online Support Account Request". However, I haven't heard from them in the last 10 days.

I would really appreciate it if you could possibly file a case from your end on my behalf to include ISF and NMF analyses in future versions of the software.

Best Regards,

Srayan Sankar Chatterjee

Srayan,

I found the case that was logged to sort out getting a support account organised - case 46667257. There was a response to this on 15th December which explained exactly what you needed to do. You then replied to the university program email on the 20th - and it's pretty likely that the folks who look after that email alias were on the Christmas break - we have very reduced staffing over the holidays - so you may not get an answer until the new year.

I would say however that your hostid is not 007f0100. That is the output of the Linux "hostid" command which is almost entirely useless (it's just the contents of a file on Linux which is easily changed); what is needed is the output of the lmhostid command on the license server; this is (in effect) the MAC address of the license server). As you were advised, you should find out the hostid of the license server from your university program administrator and you may have to get your support case logged via that individual (the universityprogram@cadence.com address should help with this in the New Year).

I cannot create a case on your behalf, sorry.

Andrew

Thank you for the detailed response. I will make the required rectifications and submit a new request.

Thank you for the detailed response. I will make the required rectifications and submit a new request.