求助用matlab画QPSK波形

boai033

设载波频率为20Hz，信息速率为2Baud,用MatLab画出QPSK信号波形。

yf2002043227

不知道原理啊

happy

1. %file name: qpsk.m
   
2. %Written by Dr. James S. Kang, Cal Poly Pomona.
   
3. %Plot of QPSK waveform and spectrum.
   
4. %d = input data such as [1 1 0 0 1 0 0 1 1 1].
   
5. %fb = data rate in bps.
   
6. %fc = carrier frequency.
   
7. %Ac = Amplitude of the carrier.
   
8. %fstart = start frequency for spectrum plot.
   
9. %fend = end frequency for spectrum plot.
   
10. %To run the program, try
    
11. % >>qpsk([1 1 0 0 1 0 1 0 1 1],500,1000,1,0,4000)  <Enter>
    
12. function[s] = qpsk(d,fb,fc,Ac,fstart,fend)
    
13. N=size(d,2);        %N = number of data bits.
    
14. if rem(N,2) == 1
    
15.         N=N+1
    
16.         d(N)=0
    
17. end
    
18. N2=N/2;
    
19. M=32;        %M = number of samples per bit duration.
    
20. tb=1/fb;tc=1/fc;
    
21. Nc=floor(M*tc/tb); %Nc = number of samples per period of carrier.
    
22. step=tb/M;        %step = sampling interval.
    
23. for j = 1:N
    
24.         if d(j) == 1
    
25.            for i = 1:M
    
26.                 m((j-1)*M+i)=1;
    
27.            end
    
28.         else
    
29.            for i = 1:M
    
30.                 m((j-1)*M+i)=-1;
    
31.            end
    
32.         end
    
33. end
    
34. for j = 1:N2
    
35.         if d(j*2-1) == 1
    
36.            for i = 1:2*M
    
37.                 mi((j-1)*2*M+i)=1;
    
38.                 si((j-1)*2*M+i)=Ac*cos(2*pi*(i-1)/Nc);
    
39.            end
    
40.         else
    
41.            for i = 1:2*M
    
42.                 mi((j-1)*2*M+i)=-1;
    
43.                 si((j-1)*2*M+i)=Ac*cos(2*pi*(i-1)/Nc+pi);
    
44. 
    
45.            end
    
46.         end
    
47.         if d(j*2) == 1
    
48.            for i = 1:2*M
    
49.                 mq((j-1)*2*M+i)=1;
    
50.                 sq((j-1)*2*M+i)=Ac*sin(2*pi*(i-1)/Nc);
    
51.            end
    
52.         else
    
53.            for i = 1:2*M
    
54.                 mq((j-1)*2*M+i)=-1;
    
55.                 sq((j-1)*2*M+i)=Ac*sin(2*pi*(i-1)/Nc+pi);
    
56. 
    
57.            end
    
58.         end
    
59. end
    
60. for k=1:M*N
    
61.         t(k)=(k-1)*step;
    
62.         s(k)=si(k)+sq(k);
    
63. end
    
64. figure
    
65. subplot(3,1,1)
    
66. plot(t,m)
    
67. grid
    
68. %xlabel('Time')
    
69. ylabel('Amplitude')
    
70. title('Input Waveform')
    
71. subplot(3,1,2)
    
72. plot(t,mi)
    
73. grid
    
74. %xlabel('Time')
    
75. ylabel('Amplitude')
    
76. title('I Channel Waveform')
    
77. subplot(3,1,3)
    
78. plot(t,mq)
    
79. grid
    
80. xlabel('Time')
    
81. ylabel('Amplitude')
    
82. title('Q Channel Waveform')
    
83. figure
    
84. subplot(3,1,1)
    
85. plot(t,si)
    
86. grid
    
87. %xlabel('Time')
    
88. ylabel('Amplitude')
    
89. title('I Channel Modulated Waveform')
    
90. subplot(3,1,2)
    
91. plot(t,sq)
    
92. grid
    
93. %xlabel('Time')
    
94. ylabel('Amplitude')
    
95. title('Q Channel Modulated Waveform')
    
96. subplot(3,1,3)
    
97. plot(t,s)
    
98. grid
    
99. xlabel('Time')
    
100. ylabel('Amplitude')
     
101. title('QPSK Waveform')
     
102. %
     
103. %Spectrum of QPSK
     
104. %
     
105. M1=64;        %M1 = number of points per lobe.
     
106. fstep=fb/M1; %fstep = freq. step.  
     
107. Nf=floor((fend-fstart)/fstep); %Nf = total number of freq. points computed.
     
108. for i = 1:Nf
     
109. f(i)=(i-1)*fstep+fstart;
     
110.         if f(i) == fc S(i)=Ac^2*tb;
     
111.         else
     
112.          S(i)=(Ac^2*tb)*(sin(pi*(f(i)-fc)*2*tb)/(pi*(f(i)-fc)*2*tb))^2;
     
113.         end
     
114. end
     
115. for i = 1:Nf
     
116. dBS(i) = 10*log(S(i));
     
117. if dBS(i) < -200 dBS(i)=-200; end
     
118. end
     
119. figure
     
120. subplot(2,1,1)
     
121. plot(f,S)
     
122. grid
     
123. %xlabel('Frequency')
     
124. ylabel('Magnitude')
     
125. title('QPSK Spectrum (Linear)')
     
126. subplot(2,1,2)
     
127. plot(f,dBS)
     
128. grid
     
129. xlabel('Frequency')
     
130. ylabel('Magnitude')
     
131. title('QPSK Spectrum (dB)')
     
132. end

复制代码

boai033

不能运行啊！！！

happy

原帖由 boai033 于 2007-6-23 20:39 发表

                               
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不能运行啊！！！

自己先学学怎么调用子程序吧
别看不看就喊

boai033

我有看啊，可是写得太专业点了吧，很多都看不懂。我以前只是学过一些简单的程序！

happy

如果连调用函数还不会，建议还是先不要做什么东西了
找本matlab基础看看怎么回事吧

boai033

我也不想做啊，可是老师布置的作业。不能不去完成啊！！