Quadrature modulation is the general technique of modulating two carriers.
Examples include Quadrature amplitude modulation, Phase-shift keying, and Minimum-shift keying.
Constellation diagrams are used to examine the modulation in the 2-D signal space.
Sending a signal by amplitude modulation consists of sending the function
where I(t) is the signal to encode and cos(ωct) is the carrier wave, ωc is the carrier frequency – one is changing the amp...
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Quadrature modulation is the general technique of modulating two carriers.
Examples include Quadrature amplitude modulation, Phase-shift keying, and Minimum-shift keying.
Constellation diagrams are used to examine the modulation in the 2-D signal space.
Sending a signal by amplitude modulation consists of sending the function
where I(t) is the signal to encode and cos(ωct) is the carrier wave, ωc is the carrier frequency – one is changing the amplitude of a carrier wave to encode the signal, hence amplitude modulation.
In general one could also change the phase of the carrier wave, as in phase modulation – there is a dimension of phase that is not being used. In fact, one can encode another signal that is 90° out of phase by using a sine wave, as in:
this 90° (the angle of a rectangle, or a 1/4 turn) is why it is called "quadrature" modulation, and the symbols I(t) and Q(t) indicate the "in-phase" signal and "quadrature" signal.
In terms of Euler's formula, e = cost + isint, amplitude...
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