As has been pointed out a single side
band is sufficient to convey information to the distant
receiver. This reduces the power and bandwidth requirements
considerably. Moreover, the suppressed side bands may
be used as a second independent communication channel.
Filter method
of producing SSB/SC signals
A simple arrangement to produce SSB/SC
signals as it is used for filtering out one of the side
band alone. The arrangement is shown in above illustration.
However, in practice, it is difficult to design a filter
with sharp cut - off on either side. If the bandwidth
is reduced in an effort to eliminate the unwanted side
band, such a filter will introduce attenuation in the
wanted side band also. Increasing the bandwidth may
result in passing some of the unwanted side bands to
the output.
Another way of producing a SSB/SC signal is termed as
Phase Shift Method and employs two balanced modulator
illustrated below. The balanced modulator 1 is given
the modulating and carrier signals in the usual manner.
The balanced modulator 2 is given these signals after
a phase shift of 90o. If the carrier and
modulating signals are assumed to be Ec sin
ct
and Em sin mt,
then the output of the balanced modulator 1 is same
as given in the illustration below.
i.e.
But input to balanced modulator 2 is
Ec cos ct and
Em sin mt.
Therefore, the output of this circuit is given by the
product term of these two signals.
Phase
shift method of generating SSB/SC signals
When these two voltages are added in
the adder circuit, the upper side band vanishes. Leaving
aside the low side - band alone.
ct
and Em sin 
