Pulse Amplitude Modulation (PAM)

Hi. I'm trying to figure out whether the RF carrier in PAM can avoid touching zero volts.

If you set a DC bias on the modulating signal (pulses) the voltage can be made to never reach zero. The pulses derived from sampling will all be positive or negative. If you don't have a DC bias, the modulating signal (pulses) can touch zero volts. Okay, but, I'm wondering this: How do you avoid a modulated carrier (using PAM) achieving zero voltage? That would mean the carrier never vanishes. If we were talking about analogue amplitude modulation, the way we would achieve this result is to reduce the modulation index. Only at 100% modulation would the carrier disappear. I suppose the same is true of PAM. That you avoid the carrier reaching zero, by adjusting the modulating index, and not by any selection of the type of modulation, i.e. single or double polarity. Is this right? Thanks. Rich

 

If you multiply the pulse with a carrier signal you will have a sinusoid with different amplitudes depending of the pulse amplitude. If the pulse amplitude is 0, then will be the carrier sine wave.

If you want to avoid 0 V don't use 0 V amplitud. That's it.