Matlab中求功率譜密度的代碼

1、 code clear;%隨機(jī)產(chǎn)生長度大于1000的0、1信號(hào)序列，對(duì)其進(jìn)行QPSK調(diào)制%定義待仿真序列的維數(shù) Nglobal NN=2000;%定義產(chǎn)生1的概率為 pglobal pp=0.5;%產(chǎn)生隨機(jī)二進(jìn)制序列s_qpsk=randsrc(1,N,1,0;p,1-p);%畫出生成的隨機(jī)序列圖figure(1);stem(s_qpsk);axis(0 50 -0.5 1.5);xlabel(維數(shù)N)ylabel(信號(hào)強(qiáng)度)title(0/1等概分布的信號(hào))%*QPSK信號(hào)的數(shù)字調(diào)制*m_qpsk1,m_qpsk2=qpsk_modulation(s_qpsk);figure(2);plot

2、(m_qpsk1,m_qpsk2,r*);axis(-2 2 -2 2);title(QPSK的信號(hào)空間圖);%*插值，相鄰信號(hào)間插入7個(gè)零點(diǎn)*insert_qpsk1=upsample(m_qpsk1,8);insert_qpsk2=upsample(m_qpsk2,8);%畫出插值后的序列figure(3);subplot(2,1,1);plot(insert_qpsk1(1:90),ro);axis(0 100 -1.5 1.5);hold on;plot(insert_qpsk1(1:90);xlabel(實(shí)部信號(hào));axis(0 100 -1.5 1.5);title(QPSK插值后

3、序列);subplot(2,1,2);plot(insert_qpsk2(1:90),yo);axis(0 100 -1.5 1.5);hold on;plot(insert_qpsk2(1:90);xlabel(虛部信號(hào));axis(0 100 -1.5 1.5);%*升余弦濾波器濾波*out_qpsk1=rise_cos(insert_qpsk1,N,8*N);out_qpsk2=rise_cos(insert_qpsk2,N,8*N);%畫出濾波后的信號(hào)figure(5);subplot(2,1,1);n=1:100;plot(n,out_qpsk1(1:100),.-r);hold o

4、n;m=25:104;stem(m,insert_qpsk1(1:80),o);legend(濾波輸出信號(hào),輸入信號(hào));title(通過平方根升余弦濾波器濾波得到QPSK實(shí)部輸出信號(hào)（10個(gè)周期）);subplot(2,1,2);plot(n,out_qpsk2(1:100),.-r);hold on;stem(m,insert_qpsk2(1:80),y);legend(濾波輸出信號(hào),輸入信號(hào));title(通過平方根升余弦濾波器濾波得到QPSK虛部輸出信號(hào)（10個(gè)周期）);%*輸出信號(hào)眼圖*%濾波后兩路信號(hào)合并，表達(dá)成復(fù)數(shù)形式eyediagram(out_qpsk1,5*8);title(QPSK實(shí)部眼圖);eyediagram(out_qpsk2,5*8);title(QPSK虛部眼圖);%*輸出信號(hào)功率譜密度*out_qpsk=out_qpsk1+i*out_qpsk2;R_I=xcorr(out_qpsk);power_qpsk=fft(R_I);figure(8);plot(10*log10(abs(power_qpsk(1:(length(power_qpsk)+1)/2)-max(10*log10(abs(power_qpsk(1:(length(power_qp