I hoped you'd agree this way, Geoffrey_Coram !
Now the direct use of this tool is analyzing PLL output signals.
Here's the result of the frequency simulation (input signal: sin 1kHz)
In pink, the Eldo FFT (.OPTFOUR TSTART=0 TSTOP=(15m) NBPT=(1024*2048) INTERPOLATE=1)
In blue, the EZWave FFT (TSTART=1.25m TSTOP=14.25m NBTP=1048576 -> sampling frequency ≈ 80MHz)
If I calculate the harmonic distorsion with both methods... the result isn't quite the same !
The growth of the harmonic level still a problem...
Any idea ?Thanks again for your help, Geoffrey_Coram !