What is Modulation?
Modulation is a mathematically complex subject which is difficult to explain quantitatively because it is easy to get lost in all of the formulas. Fortunately, it is simple to visually understand, which is how it is covered here.
Earlier, I described a digital signal as "riding on the back of the RF." Modulation is the way the information signal (analog or digital) is made to ride on the back of the carrier signal (the RF). This is done by taking the RF signal and superimposing the information signal onto it. The act of superimposing the information signal onto the RF (carrier) signal is called modulation, and the device which does the superimposing is called a modulator. In RF systems, the RF first gets modulated ...