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PSS problem in VCO design

March 25, 2014, 2:58 am
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Hello all,

I am trying to design VCO with feedback topology (common source amplifier + pi-feedback) i.e Hartley oscillator with active inductors. First I designed a circuit with all passive components in feedback and that works fine in all PSS and PNOISE etc. Now I replaced both the inductors of feedback with active inductors and PSS doesn't work at all. I don't know whether it is a problem with my circuit or some special settings are needed, the error in PSS is like:

Error found by spectre at time = 121.667 ns during periodic steady state analysis 'pss'.

V(net0209) is too small to reliably detect the period of the oscillation. This may be because nodes with insignificant signal levels were chosen or it may be because the oscillator was never properly started.

I am using Virtuoso front to back design environment (IC 5.1.41) and simulator is spectre (not spectreRF). Here I am attaching the circuit of my oscillator where L1 and L2 are active inductors.
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Phase Noise Simulations of Frequency Multipliers Using Jitter/Timedomain Noise

April 1, 2014, 8:28 am
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Hello All,

I have simulated the phase noise of frequency dividers in the past numerous times using the method defined in Chapter 6 of "Predicting the Phase Noise and Jitter of PLL-Based Frequency Synthesizers" by Ken Kundert.

I believe that I could use the same method to run the phase noise on a frequency multiplier, but I'm having trouble finding a reference.  Do you have experience running phase noise simulations on frequency multipliers, or know of a reference?  Am I running the multiplier phase noise correctly?

I'm basically following the directions as described in the frequency divider chapter (Chapter 6) with a couple changes.  I'm doubling a 100MHz input to a 200MHz output.  The beat frequency is 100MHz, and I'm doing a relative sweeptype in pnoise and looking at the noise at the 2nd harmonic.  Other than that, I believe the method is the same.  I define a zero crossing in pnoise and look at the noise there.  From there, I calculate the phase noise from the output frequency, the slew rate at the zero crossing, and the zero-crossing noise.

Thanks in advance for your help,
Dave

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plot operating region as a function of bias voltage

March 31, 2014, 1:36 am
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 Hi again.

I am trying to plot the operating region of a MOSFET as AFUNCTION of bias voltage. Is there a way to do that?

Thanks.

 

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Insufficient memory to run PSS analysis - how to resolve?

March 6, 2014, 7:52 am
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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.

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HBAC analysis issue, while simulating a mixer from Cadence examples

April 2, 2014, 6:53 am
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Hello, 

I am having two errors in setting up the HBAC analysis. I am trying to run simulations described in Cadence examples/RFworkshop/docs for a mixer.

HB analysis runs smoothly, but when I try to run the HBAC - I get the following messages:

ERROR (SFE-874): "input.scs" 76: Unexpected identifier "annotate". Expected equals.

ERROR (SFE-678): "input.scs" 76: Statement is not in Spectre format. Use `simulator lang = spice' to introduce spice language sections.

I tried changing the default setting of the Annotate Parameter in ADE->HBAC->Options form, but with no success - the same thing happens. I have set up all the other stuff as shown in Cadence example.

Could you please try to help me out and let me know how to solve these errors?

Thank you for your time.

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Complex-constant multiplier in VerilogA

January 8, 2014, 10:04 pm
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 Dear All,

I am doing a PSS+PNOISE simulation of a circuit in Spectre.

I need to multiply the output voltage of certain terminals with Complex Constant ( exp(j*pi/4)=0.707+0.707i).

This I don't want for post-processing ( which can be easily done using Ocean Script).

I want it on the fly of simulation.

Is there any ways of achieving this in VerilogA.

Kind Regards,

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OpAmp Simulation in Cadence Spectre

November 3, 2011, 8:49 am
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Hi, I have used OpAmp symbol from Solutions library (default library of cadence). As an initial step, I have simulated a basic circuit in Op Amp. But I am not getting the desired output. Moreover, I have checked the cadence simulation manual for Op Amp. I found something difference in the symbol (from Solutions library) to that of the Cadence manual. Can you please let me know where I am wrong and what needs to be corrected? Thanks, Shahnaz
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Assura Lvs Error

April 7, 2014, 6:45 am
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I'm doing Assura LVS using TSMC 65nm technology but the cadence exit with this error. 
 I don't know a reason for this error.
 
 
 
 Operating Mode: Legacy Mode is Off


Starting dfIIToVdb...
@(#)$CDS: dfIIToVdb version av4.1:Production:dfII5.1.41:5.10.41.500.6.144 08/04/2011 13:40 (dfm21ee01) $
sub-version 4.1_USR2_HF9, integ signature 2011-08-04-1344

run on nda3.unist.ac.kr from /tools/cadence/program/ASSURA41/tools.lnx86/assura/bin/32bit/dfIIToVdb on Mon Apr  7 22:28:16 2014

Initializing from libInit.il for library tsmcN65...
   --  tsmcN65_updateCDFs.il
   --  tsmcPdkParamTable.il
   --  tsmc_esti.ile
   --  /cadencePDK/TSMC65/v1.5a/tsmcN65/../skill/tsmcN65.cxt
   --  tif_tcf_crn65lp_v1.5a.cxt
   --  tsmcN65Tool.cxt
   --  tsmcN65.cxt
   --  tsmcN65_patch1.cxt
   --  tsmcDNA_utility.cxt
*WARNING* (loadContext): context tsmcN65 already loaded
Compiling rules...

WARNING Connected layer 'nplug' is being used as via in geomStamp.
WARNING Connected layer 'pplug' is being used as via in geomStamp.
WARNING Connected layer 'n_pplug' is being used as via in geomStamp.
WARNING Connected layer 'pplug' is being used as via in geomStamp.
WARNING Connected layer 'pplug' is being used as via in geomStamp.
WARNING Connected layer 'pplug' is being used as via in geomStamp.
WARNING LVS Run detected.
Non-legacy mode has been disabled for this LVS run
Checking out license for Assura_LVS 4.10 

Reading the design data...



Finished dfIIToVdb.

Building the VDB part 2 in background mode.

Building tables for LVS Preprocessing in background mode.


Starting /tools/cadence/program/ASSURA41/tools/assura/bin/vdbToCells /home/yeskang/cadence5141/temp test

Finished /tools/cadence/program/ASSURA41/tools/assura/bin/vdbToCells

Input program 'nvn' not found.
*WARNING* An error occurred during Nvn PreExtraction.
LVS preprocessing requires a successful run of Nvn.
Assura will now terminate.

*WARNING* Bad exit from child process .. 0x100


*****  aveng terminated abnormally  *****


*WARNING* aveng exit with bad status


*****  aveng fork terminated abnormally  *****

*WARNING* Status 256
*WARNING* Assura execution terminated
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n1port

April 7, 2014, 9:50 am
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Hi, can some please help me understand why my n1port properties box (pic below) doesn't look like the one in the link below? 
 
http://uuu.enseirb.fr/~bedenes/cadence/Sparametre.html 
 
As you can see it's missing the S Parameter data file field (and others) and I  haven't been able to get n1port to work when inserting the file name into the "Model name" field. 
 
(ver. 5.10.41_USR5.053107 -- 31 May 2007).
 
Thanks!
Andy 
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Plot issues in IC 615

March 23, 2014, 5:48 pm
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 I have upgraded to IC 615 from IC 613. But I am facing problems:

1. In spectre RF when I do s parameter simulation and try to plot gain circles (Ga,Gp etc) I get nothing. Noise circles work well. I can plot the gain curves wrt frequency though which shows data is available.

 2. When I plot voltage conversion gain using pac then I get bar plot by default instead of solid line curve. Also in some plots I get in powers of ten form. How can I customize the plot?

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Help me with the tool to do corner analysis ...

February 25, 2014, 11:14 pm
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using IC 5.10.40 in cadence ,, 

 

i want to do corner analysis , i studied some manuals related to this ,, but i didn't understood how to add the process corners to my simulation ,, in this window " Add process " it is not showing any files ,, please help me to proceede .. 

here i am attacthing the image also ,, pls hlep  

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how cadence do to calculate Z11 in a psp analysis

April 10, 2014, 9:06 am
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hi,   

i'm simuliting a circuit, where i connect 4 switching caps to the port, than i run a psp annalysis to get the input impedance"Z11", and i want to know how spectre do to give such result, it's for helping me understandind how the input impedance behave.

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[Help] About the simulation of Wien-bridge OSC.

April 12, 2014, 3:25 am
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The Wien-bridge OSC is as below.

R=1K Ohms, C=1uF, so f=1/(2*pi*R*C)=159Hz. And the BW of the operational amplifier is 9KHz. Theoretically, the OSC outputs a sine wave.

However, the OSC keeps a common voltage, which is another steady state.

Is there something wrong with my simulation setup? Can you help me, please? Thanks a lot.

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ERROR (SPECTRE-4080): There are no components in the circuit.

April 15, 2014, 5:24 am
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Dear Friends,

I use Cadence Virtuoso version 6.1.5 with Spectre MMSIM 071.
I tried to simulate a simple circuit by it. But I have faced this problem:

Loading /opt/spectre/MMSIM071/tools.lnx86/cmi/lib/5.0/libinfineon_sh.so ...
Loading /opt/spectre/MMSIM071/tools.lnx86/cmi/lib/5.0/libphilips_sh.so ...
Loading /opt/spectre/MMSIM071/tools.lnx86/cmi/lib/5.0/libsparam_sh.so ...
Loading /opt/spectre/MMSIM071/tools.lnx86/cmi/lib/5.0/libstmodels_sh.so ...

/usr/lib/gcc/i586-suse-linux/4.4/cc1: /opt/spectre/MMSIM071/tools/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by /usr/lib/libppl_c.so.2)
/usr/lib/gcc/i586-suse-linux/4.4/cc1: /opt/spectre/MMSIM071/tools/lib/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by /usr/lib/libppl_c.so.2)
/usr/lib/gcc/i586-suse-linux/4.4/cc1: /opt/spectre/MMSIM071/tools/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by /usr/lib/libppl.so.7)
/usr/lib/gcc/i586-suse-linux/4.4/cc1: /opt/spectre/MMSIM071/tools/lib/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by /usr/lib/libppl.so.7)
/usr/lib/gcc/i586-suse-linux/4.4/cc1: /opt/spectre/MMSIM071/tools/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by /usr/lib/libgmpxx.so.4)

Error found by spectre during initial setup.
    ERROR (SPECTRE-4080): There are no components in the circuit.

Do you know how to solve it?

Thanks in advance
Shaa
 

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PSS simulation for RF LO and mixer simultaneously

April 15, 2014, 11:00 am
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 Dear Team,

 I am designed RF receiver in cadence. I have simulated oscillator and mixer individual. Now i am trying to simulate simultaneously. But PSS analysis is not running. Because beat frequencies for RF signal, LO signal and IF signal is different. How can i simulate it? Can you please guide me? 

 Regards,

Darshak

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Double Exponential Current Pulse In Virtuoso

April 17, 2014, 7:12 pm
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Sir,

Is it possible to model a double exponential current pulse ( used for representing Single Event Itransients) in Cadence Virtuoso?. It would be helpful if you could explain the method for getting the same.

Yours faithfully

Aravind 

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Exporting s2p file from spetre

April 20, 2014, 12:18 am
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 Hi,

I am using IC 6.1.6 and I want to export .s2p file after s parameter simulation. I tried using 

sparameter analysis window>options>output parameters >filename.s2p>dtft=touchstone

But no file is saved when I run the simulation. 

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How to calculate the capacitance of a Varactor?

April 20, 2014, 7:06 am
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Two different methods give me different curves (Cap. vs DC bias voltage). However, initial value, final value and also the capacitance at zero bias voltage for both methods are the same.

I use ADE L to calculate the capacitance of a varactor in a desired frequency. The first method was to use AC analysis. Taking the imaginary part of the current and dividing by frequency(rad/s) is the capacitance calculated by this method. The other method was to simply using SP analysis and then the imaginary part of Y11 divided by frequency(rad/s) would be the capacitance. I sweep the DC voltage across the capacitor and get the same final and middle values from both methods. However the slope of the curve is about 1.9 times different and I cannot guess why and which one I can trust.

Any idea? 

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plot operating region as a function of bias voltage

March 31, 2014, 1:36 am
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 Hi again.

I am trying to plot the operating region of a MOSFET as AFUNCTION of bias voltage. Is there a way to do that?

Thanks.

 

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spectre , multiple model files and mixed section names

March 19, 2014, 5:56 am
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Hi there,

We have a case where we have to use multiple model files in spectre simulation.

I want to avoid situation where by mistake different section names are used in the simulation.

E.g.

...
include "/home/predamar/tests/spectre/my_models/include.scs" section=fast
include "/home/predamar/tests/spectre/basic/include.scs"
include "/home/predamar/tests/spectre/my_models_2/include.scs" section=nom
...

In one place is used "fast", in other is "nom".

 I want to have the possibility to provide an error message and to stop the simulation.

The include lines which have no "section" will be ignored.

So, all the included files should have the same section name.

The only solution that I see now is to trigger a script before starting spectre simulation,and to parse the top netlist file.

I want to know if spectre has something builtin that may help.

 

Best Regards,

Marcel
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