Bandwidth of Transmission System

BANDWIDTH

The frequency range over which the baseband signals or the information signals such as voice, music, picture etc is transmitted is known as bandwidth. Each of these signals has different frequencies.

The type of communication system depends on the nature of the frequency band for a given signal. Bandwidth gives the difference between the upper and lower frequency limits of the signal. It can also be defined as the portion of the electromagnetic spectrum occupied by the signal. If ν1 and ν2 are the lower and upper-frequency limits of a signal, then the bandwidth, BW = ν2 – ν1.

BANDWIDTH OF TRANSMISSION SYSTEM

The range of frequencies required to transmit a piece of specified information in a particular channel is called channel bandwidth or the bandwidth of the transmission system. This corresponds to the spectrum that is assigned to be used by the system. For example, amplitude modulation system requires a channel bandwidth of 10 kHz to transmit a 5 kHz signal, whereas a single side-band system requires only a 5 kHz channel bandwidth for the same 5 kHz signal. This is because in amplitude modulation, the channel bandwidth is twice the signal frequency. Therefore, it is required to reduce the channel bandwidth to accommodate more number of channels in the available electromagnetic spectrum. In some applications, modulation is selected based on this.