Modulation techniques overview

- overview of the various modulation techniques that can be used for radio frequency carriers used for radio communications applications.

Today vast amounts of information are communicated using radio communications systems. Both analogue radio communications systems, and digital or data radio communications links are used. However one of the fundamental aspects of any radio communications transmission system is modulation, or the way in which the information is superimposed on the radio carrier.

In order that a steady radio signal or "radio carrier" can carry information it must be changed or modulated in one way so that the information can be conveyed from one place to another. There are very many ways in which a radio carrier can be modulated to carry a signal, each having its own advantages and disadvantages. The choice of modulation have a great impact on the radio communications system. Some forms are better suited to one kind of traffic whereas other forms of modulation will be more applicable in other instances. Choosing the correct form of modulation is a key decision in any radio communications system design.

Basic types of modulation

There are three main ways in which a radio communications or RF signal can be modulated:

• Amplitude modulation
• Frequency modulation
• Phase modulation

Each type of modulation has its own advantages and disadvantages, and accordingly they are all used in different radio communications applications.

In addition to the three main basic forms of modulation or modulation techniques, there are many variants of each type. Again these modulation techniques are used in a variety of applications, some for analogue applications, and others for digital applications.