MATLAB机考样题(带答案)Word文档格式.doc
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MATLAB机考样题(带答案)Word文档格式.doc
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(2)WriteaMATLABprogramtocomputeandplottheimpulseresponseofacausalfinite-dimensionaldiscrete-timesystemcharacterizedbyadifferenceequationofthefollowingform:
N=input('
inputthepointsyouwant:
'
);
num=[1.80.34-1.32-0.86];
den=[10.30.5-0.72];
[H,w]=freqz(num,den,N);
%计算frequencyresponse
plot(w/pi,abs(H));
title('
magnituderesponse'
plot(w/pi,angle(H));
phaseresponse'
N=input('
请输入你要求的点数N='
num=[1.80.34-1.32-0.86];
den=[10.30.5-0.72];
x=[1zeros(1,N-1)];
y=filter(num,den,x)
plot(0:
N-1,y)
num=[8.16.93-23.8210.5];
den=[11.520.18-0.1768];
[z,p,k]=tf2zp(num,den)
zplane(z,p);
[sos,G]=tf2sos(num,den)
(3)WriteaMATLABprogramtocomputeanddisplaythepolesandzeros,tocomputeanddisplaythesecond-orderfactoredform,andtogeneratethepole-zeroplotofaz-transformthatisaratiooftwopolynomialsinz-1.UsingthisprogramtoanalyzethefollowingG(z):
num=[8.16.93-23.8210.5];
den=[11.520.18-0.1768];
sos=tf2sos(num,den)
zplane(num,den)
(4)TrytogiveaprogramtoevaluatethefollowingDTFTintherange:
%由于用freqz计算频点至少是2个,所以至少输入两个频点
w1=input('
请输入你要计算的频点w1='
w2=input('
请输入你要计算的频点w2='
w=[w1w2];
num=[25953];
den=[545211];
h=freqz(num,den,w)
inputthepointsyouwanttocompute:
num=[25953];
den=[545211];
[h,w]=freqz(num,den,N);
subplot(2,2,1)
plot(w/pi,real(h));
grid
Realpart'
)
xlabel('
\omega/\pi'
ylabel('
Amplitude'
subplot(2,2,2)
plot(w/pi,imag(h));
Imaginarypart'
subplot(2,2,3)
plot(w/pi,abs(h));
MagnitudeSpectrum'
Magnitude'
subplot(2,2,4)
plot(w/pi,angle(h));
PhaseSpectrum'
Phase,radians'
(6)WriteaMATLABprogramtocomputeandplotthemagnituderesponseofacausalLTIdiscrete-timesystemwithatransferfunctiongivenby
num=[0.150-0.15];
den=[1-0.50.7];
[h,w]=freqz(num,den);
plot(w/pi,h)
num=0.15*[10-1];
den=[1-0.50.7];
[h,w]=freqz(num,den,512);
plot(w/pi,abs(h))
(7)ConsiderthefollowingFIRtransferfunction:
UsingMATLABtodetermineitszerolocationsandplotitsmagnitudeandphaseresponse.
h=[10.6.49-0.48-0.14-0.120.09];
figure
(1)
zplane(h,1);
[H,w]=freqz(h,1,512);
figure
(2)
plot(w/pi,abs(H))
figure(3)
plot(w/pi,angle(H))
clear;
num=[10.60.49-0.48-0.14-0.120.09];
den=[1000000];
[z,p,k]=tf2zp(num,den)%tf2zp(num,den)中num,den的长度必须相等
[H,w]=freqz(num,den);
n=0:
63;
n=n/(2*10^4);
x=4*n+cos(0.1*pi*n);
[H,w]=freqz(x,1);
magnitudespectrum'
phasespectrum'
(8)Givenasignal,whenusingasamplingfrequencyfT=20KHz,plotthemagnitudeandphasespectrumofthesampledsequence(givenlength-64).
fs=2e4;
n=(0:
63)/fs;
x=4*n+cos(0.1*pi*n);
h=fft(x,512);
2/511:
2,abs(h))
2,angle(h))
(9)designanIIRbutterworthdigitallowpassfilterwiththefollowingspecifications:
samplingrateof40kHz,passbandedgefrequencyof4kHz,stopbandedgefrequencyof8kHz,passbandrippleof0.5dB,andaminimumstopbandattenuationof40dB,plotfrequency-magnitudeandcheckifyourdesignfitsthespecification.
fs=40;
wp=4*2/fs;
ws=8*2/fs;
ap=0.5;
as=40;
Ft=40000;
Fp=4000;
Fs=8000;
deltap=0.5;
deltas=40;
wp=2*Fp/Ft;
ws=2*Fs/Ft;
[N,Wn]=buttord(wp,ws,deltap,deltas);
[num,den]=butter(N,Wn);
plot(w/pi,20*log10(abs(H)));
gainresponse'
[n,wn]=buttord(wp,ws,ap,as);
[num,den]=butter(n,wn);
plot(w/pi,20*log10(abs(h)))
axis([01-500])
axis([0wp-0.50]);
通带纹波'
axis([ws1-50-30])
阻带纹波'
(10)DesignaHanningFIRlowpassfiltermeetingthefollowingspecifications:
passbandedgefrequency=2kHz,stopbandedgefrequency=2.5kHz,passbandrippleδp=0.005,stopbandrippleδs=0.005,andsamplingrateof10kHz.Plotitsgainandphaseresponsesandcheckifitmeetsthespecifications?
ft=10;
fp=2;
Wp=2/10*pi;
Ws=2.5/10*pi;
dw=abs(Wp-Ws);
ds=0.005;
ap=20*log10(1-ds)
as=20*log10(ds)
M=3.11*pi/dw;
N=ceil(2*M+1);
Wc=(Wp+Ws)/(2*pi);
h=fir1(N,Wc,hann(N+1));
fs=2.5;
wp=2*pi*fp/ft;
ws=2*pi*fs/ft;
ap=20*log10(1-ds);
wc=(wp+ws)/2;
dw=ws-wp;
M=ceil(3.11*pi/dw);
N=2*M;
b=fir1(N,wc/pi,hann(N+1));
[h,w]=freqz(b,1,512);
plot(w/pi,20*log10(abs(h)));
plot(w/pi,unwrap(angle(h)));
figure(3)%局部放大,观察通带与阻带
axis([0wp/piap0])
axis([ws/pi1as0])
%从图中可以看出,通带和阻带中纹波都不满足要求,所以不满足指标
%as=-46.0206<
43.9所以不能用hanning窗设计
%应当用hamming或blackman窗设计
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