Modulation and demodulation are the most critical functional blocks in a communication system. The definition of modulation is to make a certain parameters (amplitude, phase or frequency) of the carrier changed same with the original modulating signal. Either analog modulation or digital modulation, the basic modulation methods are mainly three types as amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM). On the basis of these three modulation methods, a wide variety of modulations can be realized. Modulated signal is a low-frequency signal or video signal comes from the original information (such as voice, text, images, etc.). Demodulation is the reverse process of modulation; its role is extracting the original signal from a modulated wave signal. For amplitude modulation, demodulation is a extraction process which extract the original signal from the change amplitude of the modulated signal.This paper studies analog modulation which contain AM, FM, SSB DSB's modulation and demodulation. We use MATLAB to simulation then using Matlab graphical user interface (GUI) shows waveform to make us understand the process of the modulation and demodulation intuitively.
