Chapter 8 Communication Systems
1 Chapter 8 Communication Systems
Chapter 8 Communication Systems Communication Channel 信道 日日日 ■■ Source Modulator Modulated Signals 1调制器 Signals Be best suited for transmitting 2
2 Chapter 8 Communication Systems Communication Channel 信道 Source Signals Modulator 调制器 Modulated Signals Be best suited for transmitting
Chapter 8 Communication Systems Modulation: The general process of embedding an information bearing signal into a second signal Demodulation: Extracting the information-bearing signal. Amplitude Modulation (AM) Modulation Frequency modulation (FM) Phase Modulation(PM) Modulating Modulated Signal x y()=x()x() Signal Carrier C Signal Amplitude modulation
3 Chapter 8 Communication Systems Modulation : The general process of embedding an information -bearing signal into a second signal. Demodulation : Extracting the information-bearing signal. Modulation : Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM) Modulating Signal Carrier Signal Modulated Signal x(t) y(t) = x(t)c(t) c(t) Amplitude Modulation
Chapter 8 Communication Systems 58.1 Complex Exponential and Sinusoidal Amplitude Modulation 1. c(o=el 2. c(t)=cos@ t t Envelope 4
4 Chapter 8 Communication Systems §8.1 Complex Exponential and Sinusoidal Amplitude Modulation 1. ( ) c j t c t e = 2. cos ( ) c c t t = t x(t) t y(t) Envelope
Chapter 8 Communication Systems 58.2. 1 Synchronous Demodulation O Complex Exponential Carrier ∞→·y() Communication( LPF x channel (a2+b) e (n+) Transmitter Receiver Modulation Synchronous Demodulation 1. Suppose the modulator and demodulator are not synchronized in phase. 2. Suppose the modulator and demodulator are not synchronized in frequency. 5
5 Chapter 8 Communication Systems 1. Suppose the modulator and demodulator are not synchronized in phase. ① Complex Exponential Carrier §8.2.1 Synchronous Demodulation j t ( c c ) e + x(t) y(t) Communication Channel Transmitter Modulation Receiver Synchronous Demodulation LPF x(t) w(t) j t ( d ) e − + 2. Suppose the modulator and demodulator are not synchronized in frequency