Hi Anoop Varma m,

I was able to run the AC analysis and have the plots for the vanalyzer1 and vanalyzer2.

Note that V1 value is changed to AC 1 for AC analysis.

Hi John Kevin,

Thank you for the replay, I want CM DM separate graph(FFT analysis). please find the attached sample.

this is from the ADI article "How to Get the Best Results Using LTspice for EMC Simulation—Part 1 "

Hi Anoop Varma m,

I hope this can help you.

I tried this step by step procedures

1. Run the transient analysis and plot the vanalyzer1 and vanalyzer2

2. Go to VIEW menu and select FFT

3. Select OK

4. Select OK

Results to this


5. Add a plot pane and perform the mathematical operation to get the VCM and DCM




Final Result:

Hi John Kevin,

Thanks for your reply, Please support the below method also.

The technical note- they mentioned the EN55022 Emission Limit Lines program, the same way I made the PLT file and added it to the Ltspice plot setting, but it shows a syntax error.

In the Below video, they explain the methods. 

1)https://www.youtube.com/watch?v=Ofnyqd-yl9o

Thank you for sharing this link!

This is what I am able to generate so far.



I'm figuring out how to show the X-axis up to 30MHz.


Here is the *.plt

[FFT of time domain data]
{
Npanes: 1
{
traces: 2 {2,0,"(V(vanalyser2)+V(vanalyser1))*0.5*1e6"} {2,0,"(V(vanalyser2)-V(vanalyser1))*0.5*1e6"}
X: ('M',0,9000,0,30e+06)
Y[0]: (' ',0,0.0001,20,1e+006)
Y[1]: (' ',0,-450,50,100)
Log: 1 2 0
GridStyle: 1
PltMag: 1
Line: "dB" 4 0 (9000,316227.766016838) (50000,316227.766016838)
Line: "dB" 4 0 (50000,316227.766016838) (50000,316227.766016838)
Line: "dB" 4 0 (50000,316227.766016838) (150000,10000)
Line: "dB" 4 0 (150000,10000) (150000,1995.26231496888)
Line: "dB" 4 0 (150000,1995.26231496888) (500000,630.957344480193)
Line: "dB" 4 0 (500000,630.957344480193) (5000000,630.957344480193)
Line: "dB" 4 0 (5000000,630.957344480193) (5000000,1000)
Line: "dB" 4 0 (5000000,1000) (30000000,1000)
}
}

Hi John Kevin,,

Thanks a lot, it is working now.

If you have  EN55032 setting, please share

One thing I like to do is to convert the DM and CM noise plots to dBuV with behavioral sources in the schematic.  That way, it's obvious what the 500000*V... actually means and it avoids having to manually edit the plot expression each time.

circuit5Soln_dBuV.asc

Hi MTF_Walker, would you be able to explain why the input voltage source is pulsed, rather than keeping it at a regular constant 24VDC?

Hi WM604,

That's from the original article (see figure 7).  It provides a short turn-on delay for the source before settling to the DC level.  I'm not 100% sure, as I didn't write the original article, but it's probably there to help the simulator with convergence.