Band limitation

Band-limited frequency response:
signal in baseband position
(lower limit frequency 0 Hz,
upper limit frequency B )

A function (e.g. an electrical signal ) is band-limited if it does not contain any frequency components above a certain limit frequency ; the band limitation sets all frequencies above this upper limit frequency to zero in the frequency spectrum. Speaking: The frequencies of the signal are "limited to a certain frequency band ". ${\displaystyle f_{\text{max}}}$

In practice, a band-limited signal is obtained as follows:

• In the case of signals in the baseband , in this case the lower limit frequency , the filtering is done by a low-pass filter . Real signals in the baseband position always have negative frequency components , for example the frequency curve of a real-valued signal band-limited with the cutoff frequency B in the illustration opposite  . ${\displaystyle f_{\mathrm {min} }=0\,{\text{Hz}},}$
• For signals in the bandpass position , in this case the lower cutoff frequency , the band is limited by a bandpass filter . Signals in the bandpass position are created, for example, by modulating a baseband signal; they kick u. a. in the intermediate frequency circle of radio receivers . ${\displaystyle f_{\mathrm {min} }>0\,{\text{Hz}},}$

literature

• Bernd Girod, Rudolf Rabenstein, Alexander Stenger: Introduction to systems theory. 4th edition. Vieweg + Teubner, Wiesbaden 2007, ISBN 978-3-8351-0176-0 .
• Martin Meyer: Signal processing: analog and digital signals, systems and filters. 4th edition. Vieweg + Teubner, Wiesbaden 2006, ISBN 978-3-8348-0243-9 .