第二章川大通信系统课件.pdf

Communication Systems Xiong Shu Hua Associate Professor College of Electronics and Information Engineering Sichuan University E-mail：xiongsh@ Communication Systems Continuous-Wave Modulation Xiong Shu-hua Chapter 2 Continuous-Wave Modulation 连续波调制 2 Communication Systems Continuous-Wave Modulation Xiong Shu-hua contents • Time-domain and frequency-domain descriptions of continuous-wave modulation AM Amplitude modulation DSB-SC SSB VSB Angle modulation FM PM • Noise performance pertaining to modulation schemes 3 Communication Systems Continuous-Wave Modulation Xiong Shu-hua 2.1 Introduction Figure 2.1 Components of a continuous-wave modulation system: (a) transmitter, and (b) receiver. In addition to the signal received from the transmitter, the receiver input includes channel noise. The degradation in receiver performance due to channel noise is determined by the type of modulation used. So, it is necessary to study various modulation types and their noise performance. 4 Communication Systems Continuous-Wave Modulation Xiong Shu-hua Basic concepts about modulation Message signal: 消息信号 Information-bearing signal ：承载信息的信号 Baseband signal ：基带信号 Modulating signal/wave ：调制信号/波 Carrier: 载波，sinusoidal wave: 正弦波 Modulated signal/wave ：已调信号/波