What Does Baseband Mean?
The word baseband has slightly different meanings or usage depending on the context, but traditionally, it is a signal at a very narrow frequency range on which data or information is superimposed and then transmitted. It is also called a lowpass signal since it can include near-zero frequencies. In this sense, a sound waveform is considered as a baseband while radio signals often rated in the megahertz levels are not considered baseband.
Techopedia Explains Baseband
Baseband has various uses in the technology industry. Depending on the context, it takes on slightly different meanings, with the commonality of it being a signal.