Dear All,
In PSP(PSS, Shooting meyhod) analysis there is one option called "Choose Harmonics" under "Select PORTS" menu.
I am NOT able to understand what is its role.
What is its use when you are already specifying the frequency Range.
I went through several Spectre docs but unfortuantely could not find/understand its exact use.
Can anybody please tell what is its role and why it is needed in PSP
Kind Regards,
Dear All,
I was trying to plot the swept DC operating points of a MOS transitor with changing some parameters of the MOS. Like I swept the Vgs of MOS and did the parametirc run on 'Length' of the MOS. (Prametric run was done by going to Tools-->Parametric Analysis).
I was able to plot the parametrically swept curves by using Result Browser of ADE like ploting Id vs Vgs for different length of the transistors. But I want to plot them in MATLAB and further process the DC operating point data. I was not able to do this in MATLAB using cdsrr() command.
However using the way Mr Andrew said in this link http://www.cadence.com/Community/forums/p/21507/1307561.aspx, I was able to plot in MATLAB. So how one can trnasport the data to MATLAB if he runs parametric analysis in ADE.
Kind regards
Hi,
I am trying to do a load-pull simulation to study the optimal load condition for a CMOS Power Amplifier. For this, I use the parametric PSS simulation with a portAdapter to traverse all possible reflection coefficients (gamma) on the smith chart. After the simulation, I use the 'Power Contours' option in the Direct-Plot form to plot the contours of all the values of gamma which result in the same output power.
Is there any way I can set up the simulation to plot constant efficiency contours or in other words contours of gamma which result in the same drain-efficiency.
Thank!
Dear All,
I want to do parametric sweep of some variables of my circuit. For example I want to find IIP3 by running PSS and PAC and I want to plot the IIP3 vs value of one parameter by sweeping that variable. This result I want to interface with MATLAB.
I went through the MATLAB Application Note at MMSIM10.1. But I couldn't find any PSS simulation based on parametric sweep.
I tried below and it did not work.
In the .scs file I wrote
sweeppss sweep param=input_power start=-50 stop=20 step=20 {
pss pss fund=800M harms=2 errpreset=conservative
+ method=gear2only tstabmethod=gear2only annotate=status
pac pac start=f2 maxsideband=2 annotate=status
}
I ran spectre filename.scs.
It actually did the parametric analysis. But when I did in MATLAB as below I got:-
RFout=cds_srr('/home/manas/work_cad/TB_DIFF_NC_LNA.raw',sweeppss_pac-sweep','RFout')
??? Undefined function or variable 'sweeppss_pac'.
RFout is the net name where the output port is connected.
Can anybody please tell the basic way of doing the parametric analysis with all type of RF MATLAB commands.
Kind Regards
Can someone explain how to work with the sparam cellview?
Hello All,
I am trying to understand how to calculate and extract the gate resistance in RFCMOS. I am using IBM90nm (cms9flp) and using nmos_rf device. BSIM4 manual lists the equations for Gate electrode resistance and Intrinsic Input Resistance (Rii). But when I do dc analysis and print operating point I dont not see the gate resistance as one of the parameters (line gm,gds etc there is no parameter called gate resistance).
So how to find the value of gate resistance in Spectre? I read from one of the papers that gate resistance can be extracted from plotiing Real(1/Y11). This makes sense but why cant spectre shows the value of gate resistance in its dc oprating point information.
Please Help !!
Thanks
Hello All,
Output parameters of spectre for BSIM4 model lists two resistances rgbi and rgbd. Spectre Manual gives same description for both of them,'Gate Bias dependent resistance'. I am not sure what these resistance are? are thse Gate resistances? Please clarify.
Thanks
Dear All,
I used the Matlab-spectre interface commmand to draw AC simulation result of SPECTRE in MATLAB.
The comand I used are belw:-
resdir = '/home/..../simulation/TB_TIA_INPUT_IMPEDANCE_TEST/spectre/schematic/psf';
signals=cds_srr(resdir,'ac-ac');
Vod=cds_srr(resdir,'ac-ac','Vod');
It looks like in MATLAB I am getting the conjugate of Vod. This I learned when I plotted 'Vod' phase and Magnitude in spectre Wave-scan.
Can anybody please tell whay it is happening so.
Kind Regards
I have two questions regarding the phase noise simulation results (PSS + Pnoise) for ring oscillators:
(1) How much the precision of the initial oscillation frequency is important in estimating phase noise ?
(2) The results that I get for the phase noise seems a bit high. I feel there is a shift up in all the frequencies. In very low frequencies (close to carrier) the phase noise is largely positive. Comparing with the analysis presented in [Abidi, JSSC 2006] the phase noise sounds very high. Does someone has any idea that what could be wrong?
The ring oscillator designed to oscillate at 2.4 GHz using CML gates with a tail bias current of about 200 uA.
Thanks in advance for your help.
Armin
Hi everyone,
A RLC resonant network is as Figure 1, seen at my post below.
L=1uH, C=1uF, R=100kOhms.
Source generates a sine wave signal. The source signal's frequency is 159.155kHz and its amplitude is 10V.
1. Theoretical analysis.
The resonant frequency of LC network is about 159.155kHz. Under this frequency, the LC network's AC impedance is very large, and reaches about 1.5 MOhms. So if the circuit becomes steady, Vout is about 0V, whereas Vin-Vout is almost equal to Vin.
2. Tran simulation result.
A tran simulation is implemented with Cadence Spectre. The "stop time" is set to be 1s, so that the circuit can get steady. The tran simulation result is as Figure 2, seen at my post below.
It is seen that, Vout is almost equal to Vin.
By the way, sp and ac simulations are also carried out, which all indicate the LC network has a very large impedance at 159.155kHz.
The tran simulation result is so different from the theoretial analysis, and is not consistent with sp and ac simulation results. Why?
-----------------------------------------
Hi Mr. Beckett, Thanks for your help.
Hello All,
I am trying to measure Fmax of IBM 90nm technology in cadence. I am measuring S parameters and plotting Gumx. I get Fmax around 500GHz for 90nm while reported Fmax for 90nm are around 300GHz. I am using rfmos transistor & technology uses BSIM4.4 model. I am not sure what I am doing wrong please help.
Thanks
Hi
I am a newbie. I want to plot S parameters in Cadence 6.1 . I have been trying hard but in vain. The problem is the port selection menu is not accepting any inputs from teh schematic. so it remains blank. and finally when i run the schematic then the LOG file shows that no ports detected..
What should i do?
Please Help
Hello,
As you know that there is now a cross sectional viewer button in the analogLib mtline component edit properties/add instance form. The "Display Cross Section" button becomes visible when the Type of Input is set to Field Solver. The issue is that when I click on "Display Cross Section" button the IC 6.15 tool displays "Starting Displaying" .... in the CIW but does not display anything even after waiting for it to respond. What could be the issue?
Regards
A recent article at EDN gives some examples of how Rohde & Schwarz (which is where I work) uses Virtuoso-APS. It highlights some of the more advanced features of this simulator.
This question is regarding noise figure in a simple common-emitter LNA in the W-Band. There are two main simulations that I am using:
A) sp analysis with noise set to "yes" and the input/output ports specified.
B) noise analysis with the input port specified, and the output specified as a voltage between two nets: the net connected to the output port and ground.
The problem is that these simulations seem to interfere with one another. If I enable (A), (B), or (A and B), I get different noise figures. Including only A gives NF ~= 20dB. Including only B gives NF ~= 220dB (clearly not right). Including A and B gives two different noise results: the sp-simulation gives roughly 3dB higher noise figure than the noise-simulation. However, the difference is not exactly 3dB. One is around 5.5dB in-band, and the other about 8.8dB in-band.
I am wondering whether one of these methods is taking into account the input matching / reflected signals, whether they are just different definitions of the same thing, or if I just do not understand the differences between these two simulations. In any case, it seems odd how the results change dramatically for one simulation depending on whether the other is enabled.
I have printed noise summaries using both methods, and they include the same noise generators of the devices, resistances, and ports; however their absolute noise values differ across the two simulation methods--even for the same physical noise generator.
I am using Cadence 6.15 and MMSIM 10.1. (Somewhat related: Are Spectre and SpectreRF distinct products?)
Thank you for your help,
Paul
I'm running a simple circuit with PSS. I decided to compare the results to Transient, and found that they differ by a significant amount. My output amplitude is 783mV with PSS(spectre), 772mV with Transient, and 754mV with PSS(APS). I ran the transient out for a long time to make sure a steady state was reached. How do I know which is these 3 is the correct answer?
Thanks,
Steve
Dear all,
I am looking for base-emitter depletion capacitance (CjeO) and base-collector depletion capacitance (CjcO) with related paramters for the calculation of Cje and Cjc for SiGe bipolar transistor, 130nm IBM8HP process. I understand that there is a file that contains these parameters in one's installation directory. I would like to have the name of this file as well as his location for a simulation with Matlab,
Bimana
All,
I have recently installed a new Model Library, and am unable to see the DC Operating Points on the schematic diagram after clicking on Results->Annotate->DC Operating Points in Virtuoso ADE. I am using ADE 5.10 and USR6.127.
I wonder if anyone has any suggestion on how to resolve this issue.
Thank you.
Hi
I was trying to import cadence spectre values into matlab for analysis. I assumed that cadence samples a sinusoid for a given freq, for example if theoretically from transient signal of length upto 350ps i was expecting 1ps samples(sampled at 1000GhZ), ie 350 samples. But when i imported the values into MATLAB, there are hardly 80 odd values. The envelope of the wave resembles by cadence plot, but still i have lost a lot of values. Isnt the simulator trying to negate out some redundant values.
How do i change/freeze the simulator sampling time so that i recover the entire values ?
Hi all,
I was trying to save the operating points of a transistor M113, which wasinside an instance I4. I have put "save I4.M113:all" in ny saveop.scs file. but its giving a message "IM113 is not a device or subcircuit, and hence ignoring"? This is the first time i am trying to save the op of a device inside an instance. Any help will be appreciated.
thanks
vineeth