Mumbai University >IT>Sem3>Principles of Analog & Digital Communication

Marks: 5M

Year: May2015

• The noise bandwidth “$B_N$” is defined as the bandwidth of an ideal (rectangular) filter which passes the same noise power as does the real filter.

• Assume that a white noise is present at the input of a receiver (filter).

• Let the filter have a transfer function H (f) as shown in fig.

• This filter is being used to reduce the noise power actually passed on to the receiver.

• Now consider the dotted plot (ideal filter)

• The centre frequency of this ideal filter is $f_0$

• Let the bandwidth $“B_N”$ of the ideal filter be adjusted in such a way that the noise output power of the ideal filter is exactly equal to the noise output power of a real R-C filter.

  Then “$B_N$” is called as the noise bandwidth of the real filter.