通信信號分析

1、通信信號分析識別實驗通信信號分析識別實驗n非合作通信信號分析識別流程非合作通信信號分析識別流程通信信號分析識別實驗內(nèi)容通信信號分析識別實驗內(nèi)容n通信信號形式和特點通信信號形式和特點 模擬通信信號、數(shù)字通信信號仿真模擬通信信號、數(shù)字通信信號仿真n通信信號的調(diào)制識別和參數(shù)估計通信信號的調(diào)制識別和參數(shù)估計（一）通信信號形式和特點（一）通信信號形式和特點n模擬通信信號模擬通信信號 （1）AM信號信號（2）FM信號信號（3）PM信號信號n數(shù)字通信信號數(shù)字通信信號（1）ASK信號信號（2）FSK信號信號（3）PSK信號信號（4）QAM信號信號模擬通信信號模擬通信信號nAM信號形式信號形式00( )( )

2、cos()1( ) cos()ccccS tAm ttAQx tt調(diào)制信號: )(tm載波初始相位:c載波:c直流分量:0A調(diào)幅度（調(diào)制深度）Q：0( )100%m tA( )( )( )m tx tm tnFM和和PM信號信號)(cos()(cccttAtSFM：PM：( )2( )FMtKm t dt)()(tmKtPM調(diào)制信號: )(tmFMPMKK：頻偏常數(shù)：相偏常數(shù)n模擬信號特點（以含噪聲模擬信號特點（以含噪聲AM信號為例）信號為例）0( )( ) cos(2)( )ccY tAm tf tW t0( )cos(2)mm tf t例：被調(diào)制信號是例：被調(diào)制信號是050,/ 2mfpi

3、ccf500,(0,2 ) sf20002 . 0:/1:0sft SNR=0dB01A awgn 函數(shù)函數(shù)ammod 函數(shù)函數(shù)時域時域調(diào)用相關(guān)函數(shù)調(diào)用相關(guān)函數(shù)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函數(shù)函數(shù)fft 函數(shù)函數(shù)頻域頻域-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信號的解析形式或復(fù)數(shù)信號信號的解析形式或復(fù)數(shù)信號hilbert函數(shù)函數(shù)()0()( )( )1( )ccccjtjtZ tAm teQx te)()(tShilberttZnASK信號（信號（2ASK)( )() cos()nbccnS ta g tnTt10na( ):g t成型濾波器:1:bbbTfT載波初始相位:c載波:c數(shù)字通信信號數(shù)字通信信號

6、碼周期碼周期碼速率碼速率12( )() cos() cosnbnbnnS ta g tnTtb g tnTt1nnba 10nanFSK信號（信號（2FSK）dfffh/12bbf1/Tc21fff/ 2中心頻率中心頻率調(diào)制指數(shù)調(diào)制指數(shù)nBPSK信號信號( )()cos( )bcnnS tg tnTtt( )() cosnbcnS tc g tnTt11nc01)( )(1)nnnctc （或或?1 , 11 , 0nncanQPSK信號信號( )()cos( )bcnnS tg tnTtt( )nit1,.1 , 02MiiMiM=4321011100100Mapping(輸入01序列映射為

7、相位)nMQAM信號信號(M=16,64,256)( )cos() cossin() sinnnbcnnbcnnS tag tnTtbg tnTt) 1)(log,.,3, 11)(log,., 3 , 1,22MMbannnnnab1tann數(shù)字信號特點（以數(shù)字信號特點（以QPSK信號為例）信號為例）mI0,1m1,.,200例：輸入隨機(jī)比特流：例：輸入隨機(jī)比特流：碼速率：碼速率：fb=1/Tb=0.1載頻：載頻：fc=0.3 采樣率：采樣率：fs=1( )( )()cnjttbnX tg tnT e解析信號解析信號或復(fù)數(shù)形式：或復(fù)數(shù)形式：( )()cos( )bcnnS tg tnTttc

8、os( )sin( )nntjtIQ復(fù)信號dmodce函數(shù)（映射為函數(shù)（映射為IQ復(fù)信號）復(fù)信號）（或（或pskmod函數(shù)或函數(shù)或modem.pskmod函數(shù)）函數(shù)）randint函數(shù)（產(chǎn)生函數(shù)（產(chǎn)生0，1序列）序列）01002003004005006007008009001000-2-1012baseband signal in time domainsamplesIn amplitude01002003004005006007008009001000-2-1012baseband signal in time domainsamplesQn amplitude1.mapping基帶信號時域

9、基帶信號時域-0.5-0.4-0.3-0.2-0.100.10.20.30.40.5050100150200250baseband signal in frequency domainnomalized frequencyamplitudefftshift函數(shù)函數(shù)fft 函數(shù)函數(shù)基帶信號頻域基帶信號頻域2.Pulse shapping(根升余弦成型濾波器根升余弦成型濾波器)2sin(1)/cos(1)/)4g( )4(1 (4/) )Rt TRt TtRTtRTRt TR(Rolloff factor): (0R 1)脈沖成型濾波器脈沖成型濾波器0510152025303540-0.1-0.0

10、500.050.10.150.20.250.30.35n (samples) Amplitudesquare root raised cosine impulse response.rcosine 函數(shù)（產(chǎn)生濾波器系數(shù)）函數(shù)（產(chǎn)生濾波器系數(shù)）-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函數(shù)（脈沖成型）函數(shù)（脈沖成型）脈沖成型脈沖成型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帶通信號時域帶通信號時域-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帶通信號頻域帶通信號頻域-1-0.500.51-1-0.8-0.6-0.4-0.200.20.40.60.81QuadratureIn-PhaseScatter plotscatterplot函數(shù)函數(shù)星座圖星座圖數(shù)字信號其他特點數(shù)字信號其他特點n調(diào)制類型識別調(diào)制類型識別 僅從接收信號中識別是哪種調(diào)制類型僅從接收信號中識別是哪種調(diào)制類型步驟步驟 （1）提取信號特征（時域特征、頻域特征、）提取信號特征（時域特征、頻域特征、星座圖等）星座圖等） （2）分類器：構(gòu)建分類規(guī)則，自動從提取的）分類器：構(gòu)建分類規(guī)則，自動從提取的特征中識別調(diào)制類型特征中識別調(diào)制

14、類型（二）通信信號的調(diào)制識別（二）通信信號的調(diào)制識別n時域特征：包絡(luò)特征時域特征：包絡(luò)特征R)(ts假設(shè)接收的解析信號為假設(shè)接收的解析信號為接收信號包絡(luò)為接收信號包絡(luò)為)()(tsabst 包絡(luò)均值包絡(luò)均值)(tE包絡(luò)方差包絡(luò)方差var( (t)()(var(2tEtRn頻域特征：功率譜，二次方譜，四次方譜等頻域特征：功率譜，二次方譜，四次方譜等)(ts假設(shè)接收信號為假設(shè)接收信號為接收信號功率譜為接收信號功率譜為接收信號平方譜為接收信號平方譜為接收信號四次方譜為接收信號四次方譜為)()(tsfftabsY)()(22tsfftabsY)()(44tsfftabsYn例：識別BPSK和QPSK從

15、二次方譜和四次方譜的特征來識別-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參數(shù)估計參數(shù)估計 載波頻率估計、碼速率估計載波頻率估計、碼速率估計載頻估計：如載頻估計：如PSK信號，把信號變成單頻信號，利用信號，把信號變成單頻信號，利用FFT變換變換碼速率估計：如碼速率估計：如PSK信號，檢測碼元轉(zhuǎn)換點，利用信號