LTspice FFT Result Visualization Difficulty

Hi,

   I am using LTspice on the circuit EMI spectrum study. Let's say I have two waveforms for V1 and V2. I wonder if in LTspice, I can plot the FFT results for : 

   (1) V1+V2

   (2) FFT(V1) and FFT(V2) on the same figure

  I tried but it does not seem LTspice support these functions. Could anyone help me with LTspice? Thanks for help!

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  • +1
    •  Super User 
    on Jan 29, 2019 5:35 PM

    Hello Leey,

    You can do math equations like V(a)+V(b) even with the FFT results in the FFT-waveform view.
    Just enter V(a)+V(b) instead of V(a) in the FFT waveform viewer.

    The FFT is a linear process. Thus FFT( V(V(a)+V(b) ) is equal to FFT(V(a)) + FFT(V(b)).

    Helmut

Reply
  • +1
    •  Super User 
    on Jan 29, 2019 5:35 PM

    Hello Leey,

    You can do math equations like V(a)+V(b) even with the FFT results in the FFT-waveform view.
    Just enter V(a)+V(b) instead of V(a) in the FFT waveform viewer.

    The FFT is a linear process. Thus FFT( V(V(a)+V(b) ) is equal to FFT(V(a)) + FFT(V(b)).

    Helmut

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