Common used Digital Signal Modulation and Demodulation Based on MATLAB
Abstract:Digital communication and simulation of communication system than have flexibility and efficiency, and confidentiality such prominent characteristics. Digital communication system simulation analysis to system plays a more and more important role. Digital modulation is a kind of digital baseband signal of high frequency carrier of the amplitude, frequency and phase to control technology, and to make high frequency carrier of the amplitude, phase or frequency with digital baseband signal changes. In the signal with a high frequency modulation in sine signal as carrier signal. A sine signal amplitude, frequency and phase has three parameters and can be to the three parameters for modulation, respectively called an am, FM and jamming. Also can use the pulse signal as carrier signal. To the different characteristics of the pulse signal parameters demodulation, the most common is to pulse width modulation on, called the pulse width. Digital signal modulation of the three basic way, have the amplitude, frequency control and monitoring key phase monitoring. In signal demodulation signal in the first has modulated signal detection of the process is called demodulation or detection. Amplitude modulation is to make already the amplitude of a signal with the value of the modulated signal changes and therefore the amplitude modulated signal envelope shape and modulation signal consistent. As long as can be detected amplitude modulated signal that can realize the envelope demodulation. This method is called modulated envelope. After the signal detection, then the low-pass filter, half signal, can obtain modulation signal, realize demodulation.
This paper first introduced the ASK, FSK, PSK various modulation and demodulation of the principle; Second, with MATLAB simulation tools for, realize and compared the three demodulation method; Simulation can change the simulation parameters, the simulation parameters can be accordingly, time domain and frequency domain comparison analysis.
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