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LNA output noise floor at receiver front end.

April 2, 2020, 12:30 am
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Hi,

i am designing a broadband (100 MHz -6 GHz BW) receiver chain for  radar/rcs measurement tester. i will put Low noise amplifier after antenna input followed by mixed(10 MHz IF BW and digitizer.

I am facing problem regarding LAN. bandwidth of LAN is  approx 6 GHz(100 MHz-6GHz), gain 25-35 dB, with NF less than 2. I am uncertain about noise floor at the output of LNA.  I dont know exact SNR at the input of LNA but it shall be good.System operation will be on stepped CW waveform so receiver input signal will sweep over the BW and some step size.

so LNA output r noise floor will be? i assume, we can neglect thr role of input noise because it will be lesser than internal noise of LNA.

will it be LNA internal noise (Thermal noise due to BW) only ?

will it be LNA internal noise (Thermal noise due to BW)  + LAN Gain ? -78+25 =-53 dB? internal noise shall be lesser because NF is less than 3 . 

i have practically observed that that output noise floor is much lesser then even thermal noise( over LNA BW). i have gone through some tutorial where  formula says( internal noise+input noise)+gain. in  my case input noise shall be much less than theoretical internal noise. 

Thanks

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Gilbert mixer IIP3

April 6, 2020, 11:20 pm
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Hi all,

I am having trouble plotting the IIp3 of gilber RF mixer I made

I have plotted 1 dB compression point using QPSS and QPAC simulation. flo=2.42GHz and frf=2.4GHz , 20 MHz IF

However my IIp3 simulation shows strange results

QPSS and QPAC setup

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extracting s2p file

April 21, 2020, 11:04 am
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Hello, i managed to extract my S-param data into vcsv file,however i need a standart S2P file

is there a way to do it in cadence virtuoso?
Thanks.

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input output circle equivalent in cadence virtuoso

April 23, 2020, 4:07 am
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pnoise pmjitter simulation

April 24, 2020, 12:20 am
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Hi, when I applied a voltage divider implemented by two 100-ohm resistors to a 2Vpp 5GHz vsin source, the phase noise simulation using pnoise/fullspectrum with different types, jitter and source have different results. The simulated output noise results are 165.76aV2/Hz for pmjitter case, and 828.79zV2/Hz for source case. The source case result equals to the output noise calculation.

For my application, the output will be applied to driven circuits and thus pm jitter is concerned. As the pmjitter is based on the noise sampling at the threshold crossings, I was wondering how spectre gets the pmjitter resullts since sampling white noise with infinite bandwidth is impossible to my knowledge?

Interestingly, the Jee result by integration from 10kHz to 2.5GHz is ~41fs and is closed to Jee,rms from the transient noise simulation. I am also not sure how these results come and match each other. If applying the voltage divider output to drive next stages, I was wondering to what extent I can trust the input jitter from these simulations? Thank you.

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Spectre HB simulation issue

April 29, 2020, 5:16 pm
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Hi,

i'm using spectre HB simulation on PA (Power Amplifier) test_bench to perform large signal analysis (i want to plot Output power vs intput power, PAE and Gain)

Although the simulation returns no error, i still can't plot anything. seem like there is an issue with the ports i'm using. (analoglib ports)

i attach an image of my configuration so maybe you can find something helpful in it. 

thank you all for your help

best regards

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Sweep harmonic balance (hb) realibility (aging) simulation

May 5, 2020, 10:22 am
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hi everyone, 

i'm trying to create a netlist for aging simulation. i would like to simulate how power, Gain and PAE (efficiency) are inlfuenced after 3 hours

i would be grateful if someone can correct my syntax in the netlist since i'm trying to make a sweep HB  simulation where the input power is the parameter.

i did it without any error for the sp (S parameters)  simulation.

you can see the images for both sp and hb simulation netlists. (from left to right: sp aging netlist; hb aging netlist)

i will be grateful if someone can provide me some syntax advices.

thanks,

best regards

 

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The LSSP spectre simulation (Cadence 5) fails with the following error

May 9, 2020, 8:42 pm
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What is the meaning of this error?

I used already two ports (PORT1 and PORT2 for input and output, respectively.

-------------------------------------------------------------------------------------------------------------------------

Also when I apply the PSP analysis for S-parameter the value of maximum S21 value (4.75 dB) is much lower than the maximum power gain (17.6 dB).

while the same circuit is designed using  ADS program the two values are approximately the same around (17.1 dB).

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Exporting Sprobe Data to File

May 18, 2020, 12:38 pm
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Hi,

Is there a way to export the data from the Sprobe component to a file (e.g. s1p)?

Thanks

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discrepancy between spectrum peak value and calculator value in Direct Plot Form after hb simulation

May 21, 2020, 10:51 pm
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Hi, 

After running "hb simulation", when I plot a spectrum it shows multiple values at one frequency and Cadence calculator uses 2nd peak value instead of 1st peak value.

in attached figure, two different values at 1MHz, 1st peak=406.35uV and 2nd peak value=269.833uV and Cadence calculator uses 2nd peak value.

1) which value I can trust in this case? and why does calculator use 2nd peak value instead of 1st peak value?

2) in Direct Plot Form, when "frequency" is selected in sweep section it shows different peak value from "spectrum" peak value.

   in figure below, peak value from "spectrum" plot is 406uV at 1MHz and peak value from "frequency" plot is 657uV.

   What is the difference of these two values?

Thank you.

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BSIM4 import into AWR

May 27, 2020, 5:14 am
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Hello,

I am trying to import a cadence BSIM 4.4 model file (.scs) into AWR from a foundry PDK (built for Spectre RF). The parsing and symbol creation go through fine but it comes up with a load of "Variable not valid" errors. Some examples below:

"toxe_n33 - Equation Error: Variable 'dthkox@' is not valid"

Same for: mc_gl_f@, cnr_toxd@, dthkox@, cnr_n33@, etc...

I expect the Cadence environment takes care of these somehow. Wondered if anyone knows a solution for this or has come across this before.

AWR version I am using is:13.02r build 8379 Rev1 (104876) (64-bit)

Many Thanks,
Chris.

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Noise signal as input to RF receiver

June 15, 2020, 4:45 am
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Hi,

I want to give a noise signal as input to RF receiver and see its amplification and filtering at various stages of receiver chain.

How can I give noise signal (-174dBm/Hz) as input to circuit ?

If I use a PORT element terminated with 50-Ohm resistor in parallel and use noise temperature as 27 deg. C, then will this arrangement be able to generate above mentioned equivalent noise power output ?

Regards

Vipul

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*Error* eval: unbound variable - ana

June 19, 2020, 1:44 am
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Hi All

I am using IC6.1.4 and I am trying to simulate a circuit.when I choose the HB analyses in ADE,as I select one of the options of accuracy defaults  I get this error:

*Error* eval: unbound variable - ana

I don't know where it is coming from but I'm sure it's not related to my defined variables or circuit. also I had done the HB simulation for the same circuit before and there was no problem.I can't understand what caused this error.can anyone help me?

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Transient Simulation of Crystal Osc

June 22, 2020, 1:46 pm
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I'm simulating a 24MHz crystal OSC with spectre APS MMSIM/18.10.397 

I have the startup simulation and ic transient noise simulation which is working fine starting up in 5ms and oscillating without damping to zero with ic.
the problem rises when I tried to study the LDO ripples into the transient simulation using a periodic model file of the ripples in a vpwlf instance as the supply of the circuit. even if this supply is not connected to the crystal and is just present as a floating net. the crystal damps. 

is there any way to properly simulate such a circuit?

vccc1v8_ripple is present in the sch but floating:

/resized-image/__size/1080x0/__key/communityserver-discussions-components-files/33/3404.Screen-Shot-2020_2D00_06_2D00_22-at-22.41.04.png

transient noise simulation:

errpreset=conservative

noisefmin=1

noisefmax=1GHz

method=traponly

linearic=yes

oscfreq=24M

relref=alllocal

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Error in importing .brd file in Ansys HFSS

June 22, 2020, 2:30 pm
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Hello All,

I have been trying to import the .brd file to HFSS, but everytime I get error "Extracta view creation failed". I'm made sure that extracta.exe is installed in the cadence folder as well as where the board file is.

Please help if someone faced the same issue before. 

Thanks,

Pratik

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VSS CoSimulation NL_S Nonlinear frequency response

July 16, 2020, 10:51 am
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Hi,

This is regarding a problem encountered with VSS CoSimulation with circuit simulator APLAC_HB. The circuit is a simple low pass LC filter.

Basically I am not getting the same frequency response results in VSS for the Linear and APLAC Harmonic balance models (or even when regular harmonic balance is used). The circuit is shown in Fig.1 Below. The Circuit model with just AWR (non-VSS) works fine with both Aplac-HB and Linear-AC and shows identical results, this is shown in Graphs->Circuit (Fig.2).

Next the VSS simulator was used with the Linear-AC (LIN_S) Subcircuit. The VSS Model is showin in Fig.3 and the results for this in Fig.4. The blue curve in Fig.4 is the input and pink is output. Note this shows the same frequency response as the circuit simulator case.

The VSS simulaton with the Aplac-HB model is shown in Fig.5. The frequency profile shows a flat response (Fig.6). During simulation it was observed that the VSS simulator runs through the full range of frequencies and powers.

Wondered if anyone knows a solution for this. Unfortunately it won't allow me to attach the .emp file but if you need this please send me an email address.

Best Regards,

Chris.


Fig.1
Fig.1


FIg.2
Fig.2

fig.3
Fig.3


Fig.4

FIg.5
Fig.5

Fig.6
Fig.6

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This question about how can i get (old) workshop materials.

July 17, 2020, 5:39 am
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hi sir , have a nice day

1. Are your old workshop materials deleted from the site?

2. Will a new version of the workshop material be updated and deleted when it comes up?
Or are both maintained?

3. Is it not possible to obtain the deleted workshop materials?

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stb analysis outputs

July 19, 2020, 11:48 pm
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Hi,

I have a question about the stb analysis outputs in cadence.

I believe the way stb analysis works in spectre is based on Kundert's paper on small signal stability with double injection method: https://kenkundert.com/docs/cd2001-01.pdf

Unfortunately, the only output of this analysis (in the result browser) is the loopgain, although there must be much more information generated in order to arrive to this result.

If I could access the ABCD parameters mentioned in the 5th page of the original paper, I could use this information for several other purposes in our design & verification work.

I wonder if this is possible, or can be made possible?

Thanks in advance!

Tool versions I'm using:

cadence_ic: 6.1.7.500.23

cadence_spectre: 19.10.292

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Documents for using EMX for EM simulations of inductor and Transmission LIne

August 1, 2020, 8:26 am
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Dear All,

I am looking for documents (with examples) for using EMX for EM simulations of inductor and Transmission LIne.

Can anybody please point me so that I can dig into those.

Kind Regards,

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How to use a Lossless Transmission Line in Spectre Transient analysis

August 16, 2020, 1:00 am
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Dear All,

I need to simulate an ideal lossless transmission line with characteristic impedance= Z0 and delay=tau in TRANSIENT simulation.

I went through https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od0000000t1BIEAY&pageName=ArticleContent&sq=0050V000006LcCDQA0_201866111336303.

But here there is no mention of using ideal lossless transmission line with characteristic impedance= Z0 and delay=tau.

Can anybody please tell how to use an ideal lossless transmission line in Spectre Tran Simulation.

Kind Regards,

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