Base band signals produced by various information sources are not always suitable for direct transmission over a given channel. These signals are usually further modified to facilitate transmission. This conversion process is known as Modulation. In this process, the base band signal is used to modify some parameter of a high frequency carrier signal. A carrier is a sinusoid of high frequency, and one of its parameters such as amplitude, frequency, or phase is varied in proportion to the base band signal m(t).
AM and FM Waveforms
Types of Analog Modulation
1.Amplitude Modulation (Am)
2.Frequency Modulation (FM)
3.Phase Modulation (PM)
Need for modulation
1.Modulation for ease of radiation or efficient transmission (antenna size)
2.Modulation for multiplexing (simultaneous transmission of several signals)
3.Modulation to improve the signal-to-noise ratio. E.g. FM and PM
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