Composite signals
There would be no sense of sending a single sine wave from
one device to another for practical purposes as we cannot talk over telephone,
cannot watch several channels on a television, cannot transfer data between two
PCs with just one sine wave. Fulfilment of these needs are done by making one
composite wave of several sine waves to carry out proper exchange of
information. A composite signal may be considered as a signal made of many
simple sine waves with difference in either of following properties: amplitude,
frequencies, and phases as given by fourier analysis.
Bandwidth
When a number of component waves (sine waves) travel through
a channel; then their combined frequency domain diagram is obtained as follows:
The difference in the, component having the highest value of
frequency (here, 3000 Hz) and that having the lowest value of frequency (here,
1000 Hz) is termed as bandwidth of the channel (here, 2000 Hz).
Bandwidth of a periodic signal is discrete in nature and
that of a non-periodic signal is continuous in nature.
Bit rate
Bit rate is the number of data bits travelling through a
point in one second. It is expressed in bits/second.
Bit length
Bit length is the value of distance occupied by a bit on the
transmission medium. It can be obtained by the formula:
Bit length = propagation speed * bit duration
