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Insufficient memory to run PSS analysis - how to resolve?

apaj

Hello.

I did see that there are three recent threads with very similar titles, but - unfortunately, with completely different problems described.

I use up-to-date MMSIM and IC5 (2012_2013 package installed on a 32 bit machine) and I have given a swap file to the PSS analysis. I am trying to get IIP3 post-layout simulation to run for my circuit (QRC used for extraction). I want it measured at 8 and 9 GHz with 200 MHz harmonics. I do only 6 steps for signals of power in the range of -20:5 dBm.

Nevertheless, the simulation breaks telling me - insufficient memory. During the simulation, it doesn't really use the file I gave it (<path>/Desktop/pss_swap - it's always 0 bytes). What it actually does is that it creates about twenty files called pss_swap_0, pss_swap_1, and so on, each of them about 1.2 GB. And it does this for every point of calculation.

Now, my question is, is it possible (and how?) to overcome this? If I choose a higher limit for extraction my S-parameters change, so I can not go higher on this. Less than 6 points... does it really make sense? Number of harmonics must remain the same since I need it calculated at certain frequencies. 

Do you have any suggestions how to get this done?

Thank you very much for your time and effort.

Parents
  • First of all, doing multi tone simulation with harmonic balance in PSS is almost never a good idea. You can do that with shooting, because simulating a common period in the time domain will capture both frequencies and their harmonics - for hb you only get a solution including the harmonics you asked for. So in this case you'd have to simulate (say) 123 harmonics to include the effects of the third harmonic of the rf inputs, and that would be even higher with a closer spacing between the two tones.

    Instead you should use the qpss analysis in harmonic balance mode or the hb analysis with two tones (they do the same thing; two alternative interfaces to the same analysis). Then you can separately specify the number of harmonics of each tone (say 3 of each).

    Whether you will still have memory problems I can't say without seeing the &quot;circuit inventory&quot; part of the log file which will give an indication of the size of the circuit. Can you share that?

    Also, make sure you show the spectre version number shown in the log file - it is a bit strange that the terminal shows an IC5141 version of spectre.

    Regards,
    Andrew
Reply
  • First of all, doing multi tone simulation with harmonic balance in PSS is almost never a good idea. You can do that with shooting, because simulating a common period in the time domain will capture both frequencies and their harmonics - for hb you only get a solution including the harmonics you asked for. So in this case you'd have to simulate (say) 123 harmonics to include the effects of the third harmonic of the rf inputs, and that would be even higher with a closer spacing between the two tones.

    Instead you should use the qpss analysis in harmonic balance mode or the hb analysis with two tones (they do the same thing; two alternative interfaces to the same analysis). Then you can separately specify the number of harmonics of each tone (say 3 of each).

    Whether you will still have memory problems I can't say without seeing the &quot;circuit inventory&quot; part of the log file which will give an indication of the size of the circuit. Can you share that?

    Also, make sure you show the spectre version number shown in the log file - it is a bit strange that the terminal shows an IC5141 version of spectre.

    Regards,
    Andrew
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