What is "baseband"

n. 1 (context telecommunications English) The frequency range occupied by a message signal prior to modulation. 2 (context telecommunications noun adjunct English) A method of transmission in which only one frequency channel is used at a time. 3 (context electronics English) A device using baseband transmission.

Baseband is a signal that has a very narrow frequency range, i.e. a spectral magnitude that is nonzero only for frequencies in the vicinity of the origin (termed f = 0) and negligible elsewhere. In telecommunications and signal processing, baseband signals are transmitted without modulation, that is, without any shift in the range of frequencies of the signal, and are low frequency - contained within the band of frequencies from close to 0 hertz up to a higher cut-off frequency or maximum bandwidth. Baseband can be synonymous with lowpass or non-modulated, and is differentiated from passband, bandpass, carrier-modulated, intermediate frequency, or radio frequency (RF).