通信系统仿真原理与无线应用课后答案

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1、第3章采样和量化3-1答：输入：symstwXf=fourier(5*cos(6*pi*t)+3*sin(8*pi*t))输出：Xf=pi*(5*dirac(w+6*pi)+3*i*dirac(w+8*pi)-3*i*dirac(w-8*pi)+5*dirac(w-6*pi))matlab程序：t=0:0.02:8;L=length(t);xt=5*cos(6*pi*t)+3*sin(8*pi*t);f1=fft(xt);fs=10;Ts=1/fs;t1=8:-0.02:0;f=1./t1;Pt=zeros(1,L);fori=1:8:LPt(i)=1;endXst=xt.*Pt;f2=fft

2、(Xst);f3=fs*f1;f4=ifft(f3);subplot(2,2,1)plot(f,f1)axis([010-10003000])xlabel('f');ylabel('x(f)');subplot(2,2,2)plot(f,f2)axis([010-200400])xlabel('f');ylabel('Xs(f)');subplot(2,2,3)plot(f,f3)axis([010-20004000])xlabel('f');ylabel('Xr(f)');subplot(2,2,4)plot(t,f4)xlabel('t');ylabel('Xr(t)');axis([06

3、-5050])3-2答：matlab程序：t=0:0.02:8;L=length(t);xt=5*cos(6*pi*t)+3*sin(8*pi*t);f1=fft(xt);fs=7;Ts=1/fs;t1=8:-0.02:0;f=1./t1;Pt=zeros(1,L);fori=1:8:LPt(i)=1;endXst=xt.*Pt;f2=fft(Xst);f3=fs*f1;f4=ifft(f3);subplot(2,2,1)plot(f,f1)axis([010-10003000])xlabel('f');ylabel('x(f)');subplot(2,2,2)plot(f,f2)axis([

4、010-200400])xlabel('f');ylabel('Xs(f)');subplot(2,2,3)plot(f,f3)axis([010-20004000])xlabel('f');ylabel('Xr(f)');subplot(2,2,4)plot(t,f4)xlabel('t');ylabel('Xr(t)');axis([06-5050])3.5信号，（a）信号的动态范围为。（b）信号的波峰因素为。其中，S为信号的功率，所以。（c）信噪比，以dB为单位，当比特时，计算得3.11k=50;%samplesperlobensamp=50000;%totalfrequencysamp

5、lessnrdb=zeros(1,17);%initializememoryx=4:20;%vectorforplottingform=4:20signal=0;noise=0;%initializesumvaluesf_fold=k*m/2;%foldingfrequencyforj=1:f_foldterm=(sin(pi*j/k/2)/(pi*j/k/2))^4;signal=signal+term;endforj=(f_fold+1):nsampterm=(sin(pi*j/k/2)/(pi*j/k/2))^4;noise=noise+term;endsnrdb(m-3)=10*log

6、10(signal/noise);endplot(x,snrdb)%plotresultsxlabel('Samplespersymbol')ylabel('Signal-to-aliasingnoiseratio')三角脉冲波形的信号混叠信噪比矩形脉冲波形的信号混叠信噪比3-11答：matlab程序：k=50;nsamp=50000;snrdb=zeros(1,17);snrdb_triangle=zeros(1,17);x=4:20;form=4:20signal=0;noise=0;signal_triangle=0;noise_triangle=0;f_fold=k*m/2;forj=

7、1:f_foldterm=(sin(pi*j/k)/(pi*j/k))^2;term_triangle=(sin(pi*j/(2*k))/(pi*j/(2*k)))^4;signal=signal+term;signal_triangle=signal_triangle+term_triangle;endforj=(f_fold+1):nsampterm=(sin(pi*j/k)/(pi*j/k)