What is AM?
Amplitude Modulation is the done by modulating the Amplitude of an sinoid Carrier signal using the incoming signal.
The Carrier signal is a sinusoid with a fixed Frequency at least twice as high as the highest frequency occuring in the spectrum of the incoming signal. Usually a much higher frequency is choosen.
Amplitude Modulation schemes have been widely used in Analog Radio.
The output signal is the simple product of incoming signal and Carrier Signal with frequency f:
output(t) = input(t) * sin(f * t)
TODO: it would be nice to type formulas in TeX, is this working in this wiki?
- Sure. But some prerequisites has to be met. Perhaps ist easier to use pictures of the formula (the manual way of what the wiki does).
Special Kinds of AM
- DSSC, Double Sideband Supressed Carrier
- SSB, Single Side Band
- Residual Sideband Modulation (modulation used for analog TV applications)
- QAM, Quadrature Amplitude Modulation
it would be nice to have a picture showing how AM signals in the frequency spectrum behave and how much bandwidth they allocate. A short overview of AM-related problems would be nice, too. Has anybody of you this info handy?
what about noise sensitivity?