9.3 TYPES OF MODULATION

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9.3 TYPES OF MODULATION

In general, "modulation" can be defined as transformation of a signal. In Chapter 4, "Coding of Text, Voice, Image, and Video Signals", we studied pulse code modulation (PCM) and its derivatives. It is important to note that these are source coding techniques that convert the analog signal to digital form. In this chapter, we will study carrier modulation, which transforms a carrier in such a way that the transformed carrier contains the information of the modulating signal.

Many carrier modulation techniques have been proposed in the literature. Here, we will study the most fundamental carrier modulation techniques that are used extensively in both analog and digital communication systems.

Carrier modulation can be broadly divided into two categories:

• Analog modulation

• Digital modulation

The various analog modulation techniques are:

• Amplitude modulation (AM)

• Frequency modulation (FM)

• Phase modulation (PM)

Analog modulation techniques can be broadly divided into amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). FM and PM together are known as angle modulation techniques.

FM and PM together are known as angle modulation techniques.

The various digital modulation techniques are:

• Amplitude shift keying (ASK)

• Frequency shift keying (FSK)

• Phase shift keying (PSK)

The three digital modulation techniques are (a) amplitude shift keying (ASK); (b) frequency shift keying (FSK); and (c) phase shift keying (PSK).

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