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Printing pnoise summary from an ocean script

February 19, 2015, 12:23 pm
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Hi,

I want to print a noise summary after running noise analysis where I want to sort the top 50 noise contributors but sort them by their composite noise. 

I only see the following options in the oceanref documentation for noisesummary and I do not see an option to sort by composite noise. How do I do this using ocean?

 

noiseSummary(s_type [?result s_resultName [?resultsDir t_resultsDir]]

[?frequency f_frequency] [?weight f_weight] [?output t_fileName | p_port]

[?noiseUnit t_noiseUnit] [?truncateData x_truncateData]

[?truncateType s_truncateType] [?digits x_digits]

[?percentDecimals x_percentDecimals] [?from f_from] [?to f_to]

[?deviceType ls_deviceType] [?weightFile t_weightFile]

[?paramValues ls_paramValues])

Regards.

Vish

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Input referred noise current through pnoise

February 25, 2015, 1:45 pm
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Hi!


I set a pnoise analysis to measure the input referred noise current of a lock-in amplifier. I used the pnoise analysis because one of the blocks that constitutes the lock-in is a Gilbert-cell mixer.


In the pnoise analysis, I set the Input Source to current in the drop down box and selected my current source at the input of the circuit, but I am only able to plot the result in V/sqrt(Hz), while I desired to plot the result in A/sqrt(Hz). Am I missing something?

The setup is attached.


Thanks!

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Explanation for ocean expression for phase noise

March 1, 2015, 7:34 pm
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Hi ,


What does 5 in the phase noise expression  means ?

Phase\ Noise\;\ dBc\/Hz = phaseNoise(5 "pss_fd" ?result "pnoise")

Does it mean 5th harmonic relative to pss fundamental frequency ?
 What does pss_fd means ?

Thanks & Regards

Vishal

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LC parallel circuit at resonant frequency

March 2, 2015, 1:34 pm
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Dear All,

I am trying to simulate a simple LC parallel circuit when it is drived by a voltage source.

I'm expecting the current of the voltage source V1 to get smaller as its frequency gets closer to the resonant frequency.

When I simulate this circuit at the resonant frequency, with spectre default values, I get:

I tried to play around with the following parameters:

maxstep, reltol, vabstol, iabstol

without success.

My question is: how do I setup Spectre in order to get consistent and accurate results?

What I expect to see is a sine-shaped current signal with no DC value.

I'm including the netlist of the simulation shown above:

// Generated for: spectre
// Generated on: Mar 2 16:11:27 2015
// Design library name: paper3
// Design cell name: LC_osc
// Design view name: schematic
simulator lang=spectre
global 0
parameters _EXPR_8=1.986858915135295e-08 C=1p L=100n vdd=1 \
freqC=503.30696M cycles=10 L_IC=-sqrt(C/L)*vdd/2

// Library name: paper3
// Cell name: LC_osc
// View name: schematic
L1 (Vin 0) inductor l=L r=1a ic=0
V1 (Vin 0) vsource type=sine freq=freqC ampl=vdd/2 sinephase=90 sinedc=0
C1 (Vin 0) capacitor c=C ic=vdd/2
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \
digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
checklimitdest=psf
tran tran stop=_EXPR_8 errpreset=conservative write="spectre.ic" \
writefinal="spectre.fc" annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
save Vin V1:p L1:1
saveOptions options save=allpub

 

Thank you in advance.

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understanding of frequency folding in Cadence pnoise set-up

March 3, 2015, 2:59 pm
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Hello, there

I went through previous discussions and try to confirm my understanding regarding pnoise simulation set-up is correct.

Let’s take an example:

 

VCO output freq = 1G Hz

Sweep Start= 200; Stop=0.5G Hz (half of fundamental freq)

Relharmum=1: it means that frequency range from 1.0000002G Hz to 1.5G Hz is output noise frequeny of interest.

 

The noise from 1.0000002 to 1.5 GHz will be directly added to output noise spectrum without conversion effect.

The noise from 200 to 0.5G Hz will be upconverted to 1.0000002 to 1.5 GHz by 1st harmonic.

 

How about the noise from 0.5G Hz to 1 GHz?

 

If by 1st harmonic: It will be converted into from 1.5G to 2GHz and from -0.5G to 0 Hz. It means that noise from 0.5G to 1GHz won’t contribute to the output noise. It seems like it is not quite right. Please help me to clarify. Thanks!

Best

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Manual for Spectre models

March 3, 2015, 4:13 pm
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Hi,

I want to map MOS Spectre models to BSIM4 models. Is there a document/userguide  for understanding Spectre models?

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problem with nodeset and ic Ringoscillator design

March 6, 2015, 12:23 am
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Hello, 

I am simulating ring oscillator to match current and frequency values from simulation run by some other ppl. Those guys used SPF spice file and I have extracted DSPF file. After running simulation I am getting slight deviation in values, in order to tackle it , I need to see the response of active devices so I comment out all parasitic capacitors and set very low resistance to parasitic resistors that it will behave as a short. The simualtion run time was 50ns and before modifying R's and C's it was taking 24 min on average, but Now in 2 days it just passed through 3ns . When I did i set the nodeset values to certain nodes, but these nodes are not added in netlist and virtuoso gives me this error :

Ensure that the specified schematic names are valid.

/I0/I3/I0/net8 /I0/I3/I0/net31

These nodes are on the first level going down to the hierarchy (descend ). If I select any node from top level then its added to the netlist. After this I creted spectre .ic file and add these nodes there with their values, and then added this file as initial condition, even then the simulation is very very slow.

Any solution or suggestion that can help me to analyse the results only from the extracted transistors in my DSPF file.

Thanks

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Problems using RFTline Lib

March 9, 2015, 11:14 am
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Does anyone have experience using the RFTline Lib in Cadence IC616?  I am trying to develop a multi-conductor transmission line model to implement in a high speed I/O design.  In the development of my model, I am simulating S-Parameter data across frequency and comparing the results with EM simulations in Sonnet.  So far my results are not agreeing, and I am not sure what I'm doing wrong.  

My goal is to characterize the the match as well as crosstalk coupling between lines.  I have used both mclin and ncline to model multi-conductor microstrip lines.  I have instantiated a stackup and defined the dielectrics and conductors as they will be physically implemented.  

The network I am modeling is illustrated in the figure below, with the exception that I am simulating 3 pairs instead of 2: 

I have set up a 6 conductor nclin and am simulating a 12 port network.  My test bench looks as such: 

The dimensions I defined are: length = 2000 mils, Ws = 2 mils, s = 2 mils, h = 2 mils, t = 0.7 mils, 2 <= Sc <= 10 mils.  These parameters correspond to the cross sectional figure above.  I am sweeping from 100M up to 60G, and varying Sc between 2, 4, 8 and 10 mils. 

The problem I am having is that when I increase Sc, the spacing between conductor pairs, my coupling performance degrades, which is opposite to what I think intuitively should happen.  As this spacing increases (approaching infinity), the performance of the line should resemble that of a single pair; however, my results do not yield this behavior.

Below are my S-parameter results, where S55 is the reverse gain (S11), S65 is the forward gain (S21), and S45 and S85 are the coupling from adjacent lines.  Notice how the line performance significantly degrades as coupled spacing increases:   

These results do not match my EM simulations, which yield an increase in performance as coupling space is increased.  Does anyone know of deficiencies with the RFTline lib or limitations to its use?  I have read through the library documentation, and I cannot find any clues that would point to this behavior.  Any input is greatly appreciated.

Cheers,

Daron 

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RLC series model in MEMS gyroscope

March 10, 2015, 7:49 am
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Hi all! I am now designing an oscillator for MEMS gyroscopes. The MEMS has an equivalent RLC series model; so i put it in a positive loop and make it oscillate. But my problem is: the equivalent inductance is of 2MH! and the equivalent capacitance is of 40aF. I see that Cadence does not simulate correctly the transient response of this RLC. I am very inexperienced about Cadence: Is there any simulation parameter to be changed in order to get a correct simulation? Thank you all for your answers
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Load-Pull Contours issue

March 13, 2015, 11:49 am
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How to add Full Spectrum Pnoise analysis in IC5141

March 17, 2015, 2:13 am
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Dear All,

I am using IC5141 and MMSIM-14.

But in GUI I am not getting the "Full Spectrum Pnoise analysis" option.

Is there any way of enabling this above option ?

Kind Regards,

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How to make a block Noise-less while doing Noise analysis in Spectre

March 17, 2015, 2:17 am
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Dear All,

I am doing Pnoise analysis of my Receiver.

I want to make some block NOT add any Noise. How this can be achieved ?

Kind Regards,

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How to see the Devices/Instances contributing to the circuit Noise Figure in Pnoise analysis

March 20, 2015, 9:34 am
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Dear All,

I am using IC5141 & MMSIM14  and I am doing Pnoise simulation for my Circuit.

Can anybody please tell how  to see the Devices/Instances LIST contributing to the circuit Noise Figure in Pnoise analysis.

Kind Regards,

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Verilog A module PSS analysis taking too much time

March 20, 2015, 2:56 pm
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Hi

I have a verilogA module of an ideal VCO, and I want to run a PSS and PNOISE analysis to see its phase noise, but the simulation time goes to several MEGA seconds. Does anyone know why and how to deal with this?

Thanks in advance

Attached is the VCO code:


`include "discipline.h"
`include "constants.h"

module VCO_ideal( in, out );
input in;
output out;
electrical in, out;
parameter real amp = 1;
parameter real center_freq = 14G;
parameter real vco_gain = 1K;
parameter integer steps_per_period = 32;

   real phase;
   real inst_freq;
   integer resetph;

   analog begin

    inst_freq = center_freq + vco_gain * V(in);
    $bound_step (1.0 / (steps_per_period*inst_freq));

    phase=idt(inst_freq,0);
    //phase = idtmod(inst_freq,0,1);
    V(out) <+ amp * sin (2 * `M_PI * phase) + amp;
   end
endmodule

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Noise summary of Pnoise is NOT showing any device in the Print LIST

March 21, 2015, 10:13 am
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Dear All,

I did a PNOISE simulation of a comparatively big circuit.

But when I tried to print the noise summary ( Results->Print->Noise Summary), it is not showing any components in the screen. ( I have done INClude All in the browser)

Could anybody please tell what is the issue ?

Kind Regards,

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Injection coupled Quadrature VCO - measuring the relative phase between the two quadrature outputs

March 24, 2015, 3:44 am
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Hi All,

I am trying to simulate a 3.6GHz injection coupled quadrature VCO. I would like to measure the relative phase between the two quadrature outputs. It can be noticed from literature that based on the topology used, coupling mechanism, couplign strength etc the relative phase difference between the two quadrature outputs can be either  +90degrees or -90degrees. 

during the design process while running PSS i have noticed that the phase difference is interchanging in the PSS solution. It is at times 90 degrees and at times -90 degrees. Since certain quadrature VCOs are know to have the possibility of oscillating with either of the phase differences I wanted to device a force start mechanism to make sure the phase difference is always the same and not varying. 

In order to have a known phase difference, one method i tried and seemed to work is to start one of the coupled oscillators before the other. I am doing this by switching on the bias current source of one of them after the other. This bias switching and settling is a slow process, takes about 10u sec. So over all i need to run the entire simulation for about 15u sec. Doing a transient is taking very long time ( i also need to run this across pvt corners, monte carlo sims etc) So i would like to know if there is a faster way to do the simulations and still get accurate results for the relative phase difference that i am trying to measure.

Thank you,

Vijay

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To see the Noise of certain Instances in the Noise Summary during PSS/PNOISE analysis

March 24, 2015, 4:23 am
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Dear All,

I want to see only the noise contribution of certain instances in NOISE SUMMARY PRINT list.

The Result->Noise summary Setting snapshot is attached in the post.

But if you see it showing a complete blank list in the result summary.

Could anybody please tell what is the issue and how to fix it ?

Kind Regards,

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Blocker Noise Figure / Reciprocal Mixing Noise test using SpectreRF (MMSIM14)

March 26, 2015, 8:28 am
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Dear All,

I want to see/simulate how a close in blocker affects my receiver noise in the presence of LO-phase noise.

I provide a square LO to my receiver Mixer and a Blocker at the receiver input.

May be I have to model the LO phase noise in Verilog-A & then do a Pnoise analysis. ( But beat frequency reduces quite considerably with respect to LO frequency because of close in Blocker )

Can anybody please comment and give suggestion how to do this type of simulation efficiently in SpectreRF  ?


Kind Regards,

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Impedance Control Tracing

March 27, 2015, 6:19 am
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I am Currently designing a 4 layer RF PCB for which I require impedance control trace for antenna connections. the two inner layers are gnd and power layers. I have knowledge that trace impedance depends of PCB material used and its thickness. Kindly guide if the inner layer used for power and gnd should be conductor /plane. Because as i change the layer type the width of the trace becomes less for 50 ohm impedance approx 10 mils. while changing them to conductor increases the trace width.

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Parametric Analysis over EM Simulated S-parameter Data

March 30, 2015, 3:56 pm
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Hi

I have employed HFSS to Em simulate some designed transmission lines with different lengths. Now I use them in Cadence-Virtuoso in NPORT and it works easily. I have named the data files such as TL100, TL105,TL110, ... and I have completed the sweep for 5u increment.

The problem is that I need to be able to sweep over these TLs. i.e. I want to be able to use ADE-L>Tools>Parametric Analysis in order to sweep over the existing lengths of the transmission line. However, in NPORT I have to type the full name of my data file and hence I have no idea how to do that.

Is there any way to do this kine of sweeping?

Thanks

Hamid

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