As indicated earlier, to retain all the relevant information in a signal to be digitized,
the sampling frequency must to two or more times the maximum frequency component in
the target signal. This requirement typically assumes that the spectrum of the signal to be
digitized ranges from DC or 0 Hz to some upper frequency fm. However, what the Nyquist
requirement really says is that all the information will be retained if the signal is sampled
at twice the bandwidth (BW) of the signal. The bandwidth of a signal is simply the difference
between the upper ( f2) and lower ( f1) frequencies dei ning the bandwidth, or