IMPORTANT POINTS TO REMEMBER
A signal generator
A signal has two important characteristics-(a) amplitude ,and (b) frequency or phase.Analog signal is a continuous function of time.It may take any value in a given range. Digital signal is a discrete signal discontinuous in time.They are sampled with time.
Bandwidth is the range over which frequencies in a signal vary
Base band is the range of frequency representing the original signal;the one delivered by source.
Modulation is the modification of a message signal by varying some of the characteristics of a wave to transmit information. The radio frequency carrier wave is superimposed by an audio frequency signal.
There are three types of modulation:
(c) Pulse modulation,
(a) Amplitude modulation: The amplitude of the carrier wave is varied in proportion to amplitude of modulating signal.
(b) Frequency modulation: The frequency of a carrier