Chapter8 CommunicationSystem 信号与系统教学课件

单击以编辑,母版标题样式,单击以编辑母版文本样式,第二级,第三级,第四级,第五级,*,8,Communication systems,8.1,Complex Exponential and Sinusoidal,Amplitude Modulation,Modulating system model:,8.,Communication Systems,x(t),c(t),y(t)=x(t)c(t),x(t) - modulating signal,c(t) - Carrier signal,8,Communication systems,8.1.1,Amplitude Modulation with Complex,Exponential Carrier,Exponential carrier:,For convenience, let,c,=0, so,Output signal,(modulated signal),:,(1) Modulation Theory,8,Communication systems,8,Communication systems,(1) Implementation,8,Communication systems,8.1.2,Amplitude Modulation with Sinusoidal signal,For convenience, choose,c,=0, so,8,Communication systems,8,Communication systems,8,Communication systems,8.2,Demodulation for Sinusoidal AM,8.2.1,Synchronous demodulation,(1),Demodulation process,8,Communication systems,In frequency domain:,In time domain:,Expected signal:,8,Communication systems,8,Communication systems,(2),Synchronous problem,8,Communication systems,Time domain:,The output of,lowpass,filter:,Ideal output: x(t),When, it is referred to as,synchronous,demodulation,.,8,Communication systems,8.2.2,Asynchronous demodulation,Amplitude-modulated signal:,8,Communication systems,8,Communication systems,Problem: 8.1 8.3 8.22 8.28,