Modulation scheme

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 transmitted information is 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, and 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

External links

• Theory behind demodulators for digital TV