Amplitude Modulation

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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.

Mathematical Setting

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).

An Example

Carrier Signal in time domain
File:AM picture4.jpg
Carrier Signal in frequency domain (to be added)
Modulating Signal in time domain
File:AM picture5.jpg
Modulating Signal in frequency domain (to be added)
AM Signal
File:AM picture6.jpg
AM Signal in frequency domain (to be added)

Special Kinds of AM

Aquired Bandwidth

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?