Modulation Techniques are methods used to encode digital information in an analog world. The 3 basic modulation techniques are:

AM (amplitude modulation)
FM (frequency modulation)
PM (phase modulation)

All 3 modulation techniques employ a carrier signal. A carrier signal is a single frequency that is used to carry the intelligence (data). For digital, the intelligence is either a 1 or 0. When we modulate the carrier , we are changing its characteristics to correspond to either a 1 or 0.

Modem Modulation - There are 3 basic types of modulation used in modems:

FSK - Frequency Shifted Keying
QPSK - Quadrature Phase Shifted Keying
QAM - Quadrature Amplitude Modulation

Modern modems use a combination of the above basic modulation techniques and compression to achieve the high data transfer rates (14.4 Kbps and up).

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Copyright July 2013 Eugene Blanchard