Modulation scheme

From LinuxTVWiki
Revision as of 07:05, 18 December 2016 by Voidxor (talk | contribs) (Add ASK and FSK.)
Jump to navigation Jump to search

The modulator converts an input signal into a form suitable for RF transmission. The demodulator recovers the original signal. Since the RF signal is a based sine wave oscillating around the transmission frequency, the modulator has to modulate this sine wave in a way so that all information is transmitted and well-recoverable but only as little bandwidth as allowed is allocated.

The more the modulation scheme modifies the original sine wave the more the frequency of the RF sine wave will vary -- the higher the bandwidth will be.


Analog modulation schemes
Shortform Name
AM Amplitude Modulation
FM Frequency Modulation
PM Phase Modulation
Digital modulation schemes
Shortform Name
ASK Amplitude Shift Keying
FSK Frequency Shift Keying
BPSK Binary Phase Shift Keying
QPSK Quadrature Phase Shift Keying
QAM-16 16-state Quadrature Amplitude Modulation
QAM-32 32-state Quadrature Amplitude Modulation
QAM-64 64-state Quadrature Amplitude Modulation
QAM-128 128-state Quadrature Amplitude Modulation
QAM-256 256-state Quadrature Amplitude Modulation
8VSB 8-state Vestigial Side Band Modulation
OFDM
DMT
Orthogonal frequency division modulation
Discrete multitone modulation

If you interested in the inner workings and the theory behind demodulators for digital TV, there are some signal processing tutorials at http://www.complextoreal.com/.