PSPICE-FOR-TI: FFT with Frequency vs Decibels for Dc circuit

Hi Misbah,

Please share your project.

https://e2e.ti.com/support/tools/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/969692/faq-pspice-for-ti-how-do-i-share-pspice-for-ti-projects?tisearch=e2e-sitesearch&keymatch=faq%252525253Atrue

Thanks,
JC

modifiedlisn-2023-06-15T14-20.zip

Hi Misbah,

I cannot simulate the sim profile "transient":

ERROR(ORPSIM-15113): Model Lbreak used by L_L1 is undefined
ERROR(ORPSIM-15113): Model Lbreak used by L_L3 is undefined

-JC

L1 and L3 are inductors from Pspice library. T

hey are the standard Lbreak inductors.

the simulation ran. can you show the FFT you did? what are the signals?

The plot window now has traces V(R64:2,R64:1) and V(R65:2,R64:1).

Thanks,
JC

what's the FFT parameters? base frequency, number of harmonics, etc.

First I took FFT of both signals and to have DB on vertical axis I use DB() function. By taking just FFT the output waveform is Freq vs voltage as in this picture.

I did not specify anything. I just took FFT from Trace menu. But I want to analyze my waveforms from 150kHz to 30MHz for conducted EMI analysis.

Hi Misbah,

Thanks. We'll take a look.

-JC

Hi Misbah,

Well, you already have decibels on y axis in your first screenshot. Why do you think the waveforms are not accurate? What were you expecting?

-JC

because these waveforms are quite different from one which I got from spectrum analyzer in lab. Is there another way to obtain db scale on y axis after FFT?

Hi Misbah,

does the transient waveform look like what you saw on the scope?

Note that your voltage goes to zero. It's not possible to show the value in decibel.

However, you can display the Y axis in logarithmic, just exclude zero:

Thanks,
JC