I have a signal from a PWM inverter that was sampled at 3,84 kHz. The PWM has a switching frequency of 5 kHz. The pwm signal is feeding an induction motor. If I low-pass filter the PWM signal it should result in a pure sinusoid: A*cos(2*pi*60*t+phi) of 60 Hz, which is the reference signal to the pwm.
But the sampling frequency fs=3.84KHz does not respect the Nyquist theorem that says that the sampling frequency should be twice the highest frequency of the signal, that is, it should be 2*5KHz = 10KHz. So the pwm signal is under-sampled.
By just filtering the sampled signal I believe that aliasing will happen. Right? Then I would not be able to obtain the purely sinusoidal reference.
If I linearly interpolate the PWM sampled signal so that it would go from fs=3.84KHz to fs=10KHz then, I would make the sampling rate equal to the Nyquist frequency. Now, if I filter it, aliasing would not happen anymore. Is this right?
If not, I was wondering if there is any way to filter the pwm signal and obtain the purely sinusoidal reference without aliasing. Interpolation? Resampling? I know a priori that the filtered pwm signal should result in a sinusoid, maybe that could help to reconstruct the sinusoid signal?
Thank you, L.