通信信号分析

1、通信信号分析识别实验通信信号分析识别实验n非合作通信信号分析识别流程非合作通信信号分析识别流程通信信号分析识别实验内容通信信号分析识别实验内容n通信信号形式和特点通信信号形式和特点 模拟通信信号、数字通信信号仿真模拟通信信号、数字通信信号仿真n通信信号的调制识别和参数估计通信信号的调制识别和参数估计（一）通信信号形式和特点（一）通信信号形式和特点n模拟通信信号模拟通信信号 （1）AM信号信号（2）FM信号信号（3）PM信号信号n数字通信信号数字通信信号（1）ASK信号信号（2）FSK信号信号（3）PSK信号信号（4）QAM信号信号模拟通信信号模拟通信信号nAM信号形式信号形式00( )( )

2、cos()1( ) cos()ccccS tAm ttAQx tt调制信号: )(tm载波初始相位:c载波:c直流分量:0A调幅度（调制深度）Q：0( )100%m tA( )( )( )m tx tm tnFM和和PM信号信号)(cos()(cccttAtSFM：PM：( )2( )FMtKm t dt)()(tmKtPM调制信号: )(tmFMPMKK：频偏常数：相偏常数n模拟信号特点（以含噪声模拟信号特点（以含噪声AM信号为例）信号为例）0( )( ) cos(2)( )ccY tAm tf tW t0( )cos(2)mm tf t例：被调制信号是例：被调制信号是050,/ 2mfpi

3、ccf500,(0,2 ) sf20002 . 0:/1:0sft SNR=0dB01A awgn 函数函数ammod 函数函数时域时域调用相关函数调用相关函数00.020.040.060.080.10.120.140.160.180.2-202information signal in time domaintime(second)amplitude00.020.040.060.080.10.120.140.160.180.2-202passband signal in time domain time(second)amplitude00.020.040.060.080.10.120.14

4、0.160.180.2-505passband signal with noise in time domain time(second)amplitudefftshift函数函数fft 函数函数频域频域-1000-800-600-400-200020040060080010000500information signal in frequency domainfrequency(Hz)amplitude-1000-800-600-400-200020040060080010000100200passband signal in frequency domain frequency(Hz)am

5、plitude-1000-800-600-400-200020040060080010000100200passband signal with noise in frequency domain frequency(Hz)amplitudeAM信号的解析形式或复数信号信号的解析形式或复数信号hilbert函数函数()0()( )( )1( )ccccjtjtZ tAm teQx te)()(tShilberttZnASK信号（信号（2ASK)( )() cos()nbccnS ta g tnTt10na( ):g t成型滤波器:1:bbbTfT载波初始相位:c载波:c数字通信信号数字通信信号

6、码周期码周期码速率码速率12( )() cos() cosnbnbnnS ta g tnTtb g tnTt1nnba 10nanFSK信号（信号（2FSK）dfffh/12bbf1/Tc21fff/ 2中心频率中心频率调制指数调制指数nBPSK信号信号( )()cos( )bcnnS tg tnTtt( )() cosnbcnS tc g tnTt11nc01)( )(1)nnnctc （或或?1 , 11 , 0nncanQPSK信号信号( )()cos( )bcnnS tg tnTtt( )nit1,.1 , 02MiiMiM=4321011100100Mapping(输入01序列映射为

7、相位)nMQAM信号信号(M=16,64,256)( )cos() cossin() sinnnbcnnbcnnS tag tnTtbg tnTt) 1)(log,.,3, 11)(log,., 3 , 1,22MMbannnnnab1tann数字信号特点（以数字信号特点（以QPSK信号为例）信号为例）mI0,1m1,.,200例：输入随机比特流：例：输入随机比特流：码速率：码速率：fb=1/Tb=0.1载频：载频：fc=0.3 采样率：采样率：fs=1( )( )()cnjttbnX tg tnT e解析信号解析信号或复数形式：或复数形式：( )()cos( )bcnnS tg tnTttc

8、os( )sin( )nntjtIQ复信号dmodce函数（映射为函数（映射为IQ复信号）复信号）（或（或pskmod函数或函数或modem.pskmod函数）函数）randint函数（产生函数（产生0，1序列）序列）01002003004005006007008009001000-2-1012baseband signal in time domainsamplesIn amplitude01002003004005006007008009001000-2-1012baseband signal in time domainsamplesQn amplitude1.mapping基带信号时域

9、基带信号时域-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100150200250baseband signal in frequency domainnomalized frequencyamplitudefftshift函数函数fft 函数函数基带信号频域基带信号频域2.Pulse shapping(根升余弦成型滤波器根升余弦成型滤波器)2sin(1)/cos(1)/)4g( )4(1 (4/) )Rt TRt TtRTtRTRt TR(Rolloff factor): (0R 1)脉冲成型滤波器脉冲成型滤波器0510152025303540-0.1-0.0

10、500.050.10.150.20.250.30.35n (samples) Amplitudesquare root raised cosine impulse response.rcosine 函数（产生滤波器系数）函数（产生滤波器系数）-0.5-0.4-0.3-0.2-0.100.10.20.30.40.50102030405060708090baseband signal of pulse shaped in frequency domainnomalized frequency01002003004005006007008009001000-0.4-0.200.20.4bassban

11、d signal of square root raised cosine pulse shaped in time domainsampleIn amplitude01002003004005006007008009001000-0.4-0.200.20.4bassband signal of square root raised cosine pulse shaped in time domainsampleQn amplitudercosflt函数（脉冲成型）函数（脉冲成型）脉冲成型脉冲成型050100150200250300350400450500-0.500.51passband s

12、ignal of pulse shaped in time domainsampleIn amplitude050100150200250300350400450500-0.500.5passband signal of pulse shaped in time domainsampleQn amplitude3.Carrier modulation带通信号时域带通信号时域-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100150200250300350passband signal of pulse shaped in frequency domainnoma

13、lized frequencyamplitude带通信号频域带通信号频域-1-0.500.51-1-0.8-0.6-0.4-0.200.20.40.60.81QuadratureIn-PhaseScatter plotscatterplot函数函数星座图星座图数字信号其他特点数字信号其他特点n调制类型识别调制类型识别 仅从接收信号中识别是哪种调制类型仅从接收信号中识别是哪种调制类型步骤步骤 （1）提取信号特征（时域特征、频域特征、）提取信号特征（时域特征、频域特征、星座图等）星座图等） （2）分类器：构建分类规则，自动从提取的）分类器：构建分类规则，自动从提取的特征中识别调制类型特征中识别调制

14、类型（二）通信信号的调制识别（二）通信信号的调制识别n时域特征：包络特征时域特征：包络特征R)(ts假设接收的解析信号为假设接收的解析信号为接收信号包络为接收信号包络为)()(tsabst 包络均值包络均值)(tE包络方差包络方差var( (t)()(var(2tEtRn频域特征：功率谱，二次方谱，四次方谱等频域特征：功率谱，二次方谱，四次方谱等)(ts假设接收信号为假设接收信号为接收信号功率谱为接收信号功率谱为接收信号平方谱为接收信号平方谱为接收信号四次方谱为接收信号四次方谱为)()(tsfftabsY)()(22tsfftabsY)()(44tsfftabsYn例：识别BPSK和QPSK从

15、二次方谱和四次方谱的特征来识别-0.5-0.4-0.3-0.2-0.100.10.20.30.40.505001000BPSK square spetra-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100150BPSK quartic spetra-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100QPSK square spetra-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100QPSK quartic spetran参数估计参数估计 载波频率估计、码速率估计载波频率估计、码速率估计载频估计：如载频估计：如PSK信号，把信号变成单频信号，利用信号，把信号变成单频信号，利用FFT变换变换码速率估计：如码速率估计：如PSK信号，检测码元转换点，利用信号