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1、2019/1/15,1,signal processing,carrier circuits,Transmission Medium (channel),carrier circuits,signal processing,output,input,Modulating signal,Modulated signal,Baseband signal,Bandpass signal,Baseband signal,Bandpass signal,Chapter5 AM,FM,and Digital Modulation System,2019/1/15,2,modulated bandpass
2、signal:,The spectrum of :,and the PSD is:,2019/1/15,3,要求：,关于模拟调制,1. 掌握 AM、DSB-SC、SSB调制原理和解调方法，会计算各种已调信号的调制效率、AM信号的调制百分比、平均功率、峰值包络功率、功率谱、带宽。了解AM、 DSB-SC信号的波形特点；,2. 了解FM、PM的各种基本概念，了解FM、PM两种调制之间的关系，会估算FM、PM信号的带宽（掌握卡森公式）。,3. 了解频分复用的基本概念。,2019/1/15,4,关于数字调制,1. 掌握 2ASK、2PSK、2FSK的调制原理和解调方法，会计算各种已调信号的功率谱、带宽
3、（包括无ISI系统）。会画2ASK、2PSK、2FSK信号波形；,2. 了解 MQAM、QPSK、 MPSK的调制原理和解调方法，了解 OQPSK 、/4QPSK、MSK 的调制原理，会计算各种已调信号(MQAM、QPSK、 MPSK、 OQPSK、/4QPSK)的功率谱、带宽（包括无ISI系统）。了解各种调制的星座图。会画 Type I MSK、 Type MSK 同相路和正交路基带波形 x(t) 、y(t) 。,2019/1/15,5,5.1 Amplitude Modulation,2019/1/15,6,一般：,Complete amplitude modulation,an enve
4、lope detector can be used to demodulating the modulated signal,2019/1/15,7,The percentage of modulation on an AM,* the percentage of positive modulation,* the overall modulation percentage,* the percentage of negative modulation,调制百分比影响功率分配,2019/1/15,8,The power allocation of AM signal and modulatio
5、n efficiency,The power allocation of AM signal,The normalized average power of the AM signal:,Often:,2019/1/15,9,Modulation efficiency,The normalized PEP of the AM signal:,2019/1/15,10,Characteristic of AM signal:,Envelope detector is used to detecting the AM signal.,The power efficiency of the AM s
6、ignal is lower.,The bandwidth of the AM signal is two times that of m(t).,2019/1/15,11,5.3 Double-Sideband Suppressed Carrier (DSB-SC),The percentage of modulation: It is infinite because of no carrier.,The modulation efficiency of DSB-SC is,2019/1/15,12,spctrum,2019/1/15,13,载波反相点,waveform:,2019/1/1
7、5,14,Modulation,Demodulation,The transmitter and receiver,2019/1/15,15,The percentage of modulation: It is infinite because of no carrier.,Characteristic of DSB signal:,2019/1/15,16,5.5 Asymmetric Sideband Signals,1.Single sideband signal (SSB),(1) Representation,The complex envelope of a SSB is:,Th
8、e single sideband signal:,2019/1/15,17,2019/1/15,18,The normalized PEP,(2) The power,The normalized average power,2019/1/15,19,(3) The receiver,a product detector:,2019/1/15,20,2019/1/15,21,（1）Phase Modulation (PM),相位偏移正比于调制信号,5.6 Phase modulation and Frequency modulation,2019/1/15,22,（2）Frequency M
9、odulation (FM),相位偏移正比于调制信号 的积分。,Instantaneous frequency deviation:,频率偏移正比于调制信号 。,2019/1/15,23,(a) PM:,(b) FM:,2019/1/15,24,（3）Bandwidth of the angle-modulated signal,B - the bandwidth of,For PM: , for FM:,Carsons rule,2019/1/15,25,（4）The spectral of PM or FM with Sinuoidal Modulation,正频,2019/1/15,26
10、,角调信号的离散载波功率：,角调信号的各次边频功率：,Summary:,不同时，载波功率和各边频功率的分配关系也发生变化。,已调后： ，载波功率 ，转变为各边频功率，而总功率不变。,角调信号的总功率：,2019/1/15,27,Generation of PM using a FM modulator,（5）The convert between FM and PM,Generation of FM using a PM modulator,2019/1/15,28,2019/1/15,29,5.7 Frequency-Division Multiplexing(FDM),1.Definiti
11、on,FDM is a technique for transmitting multiple messages simultaneously over a wideband channel.,2019/1/15,30,on-off keying (OOK) Binary phase-shift keying (BPSK) Frequency-shift keying (FSK)., 5.9 Binary Modulated Bandpass Signaling,2019/1/15,31,1. 2ASK signal (2 Amplitude shift keying),(1) Modulat
12、ion,The complex envelope:,2019/1/15,32,The PSD and bandwidth of the OOK,complex envelope:,The PSD of s(t) is,2019/1/15,33,2019/1/15,34,When we make no ISI filtering (如 作升余弦谱滤波）,Spectral Efficiency:,2019/1/15,35,(2) Demodulation,Envelope Detector,Coherent Detector,Optimum receiver-Matched Filter rece
13、iver,2019/1/15,36,2. BPSK (2PSK) (Phase-Shift Keying),(1) Modulation method 1th,Modulator:,Modulator,Polar NRZ,2019/1/15,37,信号矢量图 （星座图）：,2019/1/15,38,(2) Modulation method 2th,调制：,Polar NRZ,2019/1/15,39,Demodulator:,2019/1/15,40,(3).The PSD of the BPSK,The PSD of s(t) is,The PSD of g(t) is,By Eq. (3
14、.39b),we get:,2019/1/15,41,2019/1/15,42,When we make no ISI filtering (如 作升余弦谱滤波）,2019/1/15,43,4、2FSK (Frequency-Shift Keying),(1) Discontinuous-phase FSK,Producer of FSK,Oscillator f1,Oscillator f2,gate,gate,Inverse,Unipolar NRZ,+,FSK,2019/1/15,44,2019/1/15,45,So FSK signal can be represented as:,可
15、以看成是两个不同载频的 ASK 之和。,Frequency field,Where: B - bandwidth of m(t),2019/1/15,46,When m(t) is rectangular:,2019/1/15,47,When we make no ISI filtering (如 作升余弦谱滤波）,峰峰频偏,2019/1/15,48,(2) Continuous-phase FSK,Producer of FSK,Frequency Modulator fc,2019/1/15,49,The representation,The continuous phase,2019/1
16、/15,50,B - bandwidth of baseband signal m(t),The frequency field,Carsons rule:,When m(t) is square-wave:,2019/1/15,51,在描述FSK信号特性时，常用到两个参数：载波频率fc和数字调制指数h。,2019/1/15,52,(3) Demodulation for FSK,noncoherent detection,a.,适合于频差较大的场合,code,2019/1/15,53,b.,Frequency detector,2019/1/15,54,coherent detection,频差较大时适合,频差较小时，若
