Bonjour,
Je ne pratique pas LT Spice, mais dans Microcap je joue avec le paramètre "numer of cycle" pour la mesure de FFT.
Voici sa signification :
Simulation Cycles: This is the number of periods of the fundamental frequency that the simulation will run for. It should be long enough to get past any initial transients. A suitable number for most circuits is 3-5. Note that even though Micro-Cap might run the simulation for 3-5 cycles, it only uses the last full cycle for FFT calculations. For example, if you specified a fundamental frequency of 10Khz and 5 for this field, Micro-Cap would run the simulation for tmax = 5/F0 = 5/10K = 5*100uS = 500uS. It would then use that part of the output expression waveform from the end of the 4'th cycle (400uS) to the end of the 5'th cycle (500uS) for the FFT calculations. This truncated waveform can be seen in the third plot and is labeled Sampled Waveform.
Cela revient bien à sélectionner la période qui sera effectivement analysée, ce qui permet de voir ce qui se passe au début d'un burst ou à la fin. Très pratique !
Je ne pratique pas LT Spice, mais dans Microcap je joue avec le paramètre "numer of cycle" pour la mesure de FFT.
Voici sa signification :
Simulation Cycles: This is the number of periods of the fundamental frequency that the simulation will run for. It should be long enough to get past any initial transients. A suitable number for most circuits is 3-5. Note that even though Micro-Cap might run the simulation for 3-5 cycles, it only uses the last full cycle for FFT calculations. For example, if you specified a fundamental frequency of 10Khz and 5 for this field, Micro-Cap would run the simulation for tmax = 5/F0 = 5/10K = 5*100uS = 500uS. It would then use that part of the output expression waveform from the end of the 4'th cycle (400uS) to the end of the 5'th cycle (500uS) for the FFT calculations. This truncated waveform can be seen in the third plot and is labeled Sampled Waveform.
Cela revient bien à sélectionner la période qui sera effectivement analysée, ce qui permet de voir ce qui se passe au début d'un burst ou à la fin. Très pratique !