Figure 3-4. Example of digital .signal with interference.
system the audio channels are assigned to discrete
d. Multiplexing Techniques. In order to transfer
frequency bands just wide enough for the audio signal
multiple audio channels over a single radio link, a
being transferred. The total frequency bandwidth is the
method of combining or multiplexing the individual
sum of the total number of frequency bands desired.
channels into one transmitted signal and separating or
This signal is then transferred over a single transmitter-
de-multiplexing the channels at the receiver must be
receiver link. At the receiver, the overall signal is
used. The two most common techniques employed in
detected and the discrete frequency bands are
military communications are frequency division
separated for transfer over individual audio channels.
multiplex (FDM) and time division multiplex (TDM) (fig
3-5). While FDM is currently the prime technique for
characteristics of the interfering signal, only a few
multiplexing, there is a trend toward increasing use of
channels may be affected or the whole system may be
(1) Frequency division multiplex. In an FDM