Matlab中求功率譜密度的代碼

1、codeclear;%隨機(jī)產(chǎn)生長(zhǎng)度大于1000的0'信號(hào)序列，Xt其進(jìn)行QPS頒制%定義待仿真序列的維數(shù)NglobalNN=2000;%定義產(chǎn)生的概率為1pglobalpp=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(050-0.51.5）;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_modulatio

2、n(s_qpsk);figure(2);plot(m_qpsk1,m_qpsk2,'r*');axis(-22-22);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(0100-1.51.5);holdon;plot(insert_qpsk1(1:90);

3、xlabel('實(shí)部信號(hào)');axis(0100-1.51.5);title('QPSK插值后序列)；subplot(2,1,2);plot(insert_qpsk2(1:90),'yo');axis(0100-1.51.5);holdon;plot(insert_qpsk2(1:90);xlabel('虛部信號(hào)');axis(0100-1.51.5);%*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

4、后的信號(hào)figure(5);subplot(2,1,1);n=1:100;plot(n,out_qpsk1(1:100),'.-r');holdon;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QPS5部輸出信號(hào)(10個(gè)周期)');subplot(2,1,2);plot(n,out_qpsk2(1:100),'.-r');holdon;stem(m,insert_qpsk2(1:80),

5、9;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QPSKg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_qpsk)+1)/2);gridon;