Tài liệu Digital Transmission of Analog Data (Baseband Transmission)

Analog voice data must be translated into a series of binary digits before they can be transmitted in digital transmission system. One means of doing this is called pulse amplitude modulation (PAM).
The process of converting analog signal to digital is also known as A_to_D conversion or A/D conversion. The circuit does the conversion known as A/D converter.

In analog modulation (continuous wave modulation), some parameter of a sinusoidal carrier wave is varied continuously in accordance with the message signal.

In digital modulation (pulse modulation), some parameter of a pulse train is varied in accordance with the message signal.


Pulse modulation:

Pulse modulation can be subdivided into two groups: