Modulation

Modulation

 The FDM telefone transmission uses a kind of modulation, like many other types of trasmission.(either by air or cable) There are amplitude modulation, frequency and phase modulation ( that represent the main types of modulation ). What is modulation?

Modulation consists in modifying the characteristics of a signal, called carrier, in accordance with another signal, called modulating signal.The resulting wave form is called modulated signal. 

Modulation purpose

  To adapt the signals to the transmitting channel

1. To adapt the signal to the receiving and transmitting circuits
2. To distinguish the various signals

there are two types of modulation:

• Analogic modulation

• Digital modulation

In my opinion the most important types of modulation are amplitude end frequency modulation. Infact these two tecnologies are used in analogue and digital modulation

Fm  modulators

FM modulators are devices used for generating a frequency modulated signal. They can be of two types:

• Direct  modulators

• Indirect  modulators

 Direct  modulators

In direct modulators a frequency modulated signal is obtained by checking the carrier frequency directly through the modulating signal.

Indirect  modulators

In indirect modulators a frequency modulated signal is obtained by acting indirectly on the carrier frequency.

 Am modulators

Am modulators are devices used for generating an amplitude modulated signal. They can be of two types:

• Diode am modulators

• Transistor am modulators