qam调制技术应用及其matlab仿真themodulationtechnologyofqamandthesimulationinmatlab

qam调制技术应用及其matlab仿真themodulationtechnologyofqamandthesimulationinmatlab内容摘要：

hannel, no digital level meter in the case of analog TV Signal Level Meter can also be used to estimate the level of digital television signals, the digital signal level = simulated field intensity measured value + (5 ~ 10 dB). Digital signal level should not be adjusted too low, otherwise it would drop its antijamming capability, resulting in the image mosaic and discontinuity. QAM modulation principle Quadrature amplitude modulation QAM With two independent baseband signal with two orthogonal frequency carrier double sideband suppressed carrier amplitude modulation, the use of this spectrum of the modulated signal bandwidth at the same orthogonality to achieve two parallel digital information of transmission. The modulation is usually binary QAM (4QAM), quaternary QAM (l6QAM), octal QAM (64QAM), ..., the corresponding spatial distribution of the signal vector endpoint called Constellation, respectively, 4,16,64, ... a Vector endpoint. M and the signal level between the state M is. For 4QAM, when two equal amplitude signals, its generation, demodulation, and phase performance are related to 4PSK the same vector. QAM signals in phase and quadrature ponents, respectively, can be independently transmitted digital signal to ASK. QAM modulation and amplitude modulation is actually a bination of phase modulation, phase + amplitude state defines a number or numbers. The advantage is greater. QAM symbol rate, and thus obtain higher system efficiency .Usually determined by the symbol rate bandwidth .Therefore, the bits per symbol (basic units of information), the more the higher the efficiency. For a given system, the required number of symbols 2n, where n is the number of bits per symbol. For 16QAM, n = 4, so there are 16 symbols, each symbol represents 4 bit: 0000, 0001, 0010 and so on. For 64QAM, n = 6, so there are 64 symbols, each symbol represents 6bit: 000000,000001,000010 and so on. 3 System Simulation MATLAB, Simulink is a visual simulation tool, the toolbox offers a rich munication module, based on MATLAB / Simulink simulation of munication systems simulation module of the design process from the library of Simulink model 5 of a bination of the various modules. Design simulation model, you can use the mouse from the Simulink Library Browser window onto the model editor window, each module will be connected correctly, hit a few in the twomodule, the module parameters dialog box pops up, change the module to plete the various parameter values .System simulation model .MATLAB / Simulinkmunications toolbox Digital modulation in a variety of digital modulation / demodulation module .Of these, the passband (passband) module and baseband (baseband) of the points. Passband carrier signal included in the simulation model of the transmitter, the signal carrier frequency is usually much higher than the highest frequency. By the Nyquist sampling theorem, in order to recover the original signal at the receiving end, the simulation of the sampling frequency should be at least twice the maximum carrier frequency. If the signal frequency is high, then the simulation bees very slow or no direct puter simulation. Simulation is generally referred to as baseband lowpass, etc. follow the example of the simulation, the bandpass equivalent baseband signal, making the modulation and demodulation performance analysis with the carrier frequency and channel band has nothing to do, thereby reducing the system resources. System Simulation as follows: binary bit strea。