Editing Baseband (section)

=== Baseband signal ===
A ''baseband signal'' or ''lowpass signal'' is a signal that can include frequencies that are very near zero, by comparison with its highest frequency (for example, a sound waveform can be considered as a baseband signal, whereas a radio signal or any other modulated signal is not).<ref>{{cite book|url=https://books.google.com/books?id=deHQeNxHhyEC&dq=baseband-signal+lowpass-signal&pg=PA65|title=Communication System Design Using Dsp Algorithms: With Laboratory Experiments for the TMS320C30|author=Steven Alan Tretter|publisher=Springer|year=1995|isbn=0-306-45032-1}}</ref>

A ''baseband [[bandwidth (signal processing)|bandwidth]]'' is equal to the highest frequency of a signal or system, or an upper bound on such frequencies,<ref>{{cite book | title = Information, Transmission, Modulation and Noise: A Unified Approach to Communication Systems | author = Mischa Schwartz | publisher = McGraw-Hill | year = 1970| isbn = 9780070557611 | url = https://books.google.com/books?id=-gkjAAAAMAAJ&q=baseband-bandwidth }}</ref> for example the upper [[cut-off frequency]] of a [[low-pass filter]]. By contrast, [[passband]] bandwidth is the difference between a highest frequency and a nonzero lowest frequency.