有GG叫我把我的编程发出来，错了不要怪我

正确与否没有保障欢迎抛砖



做了的接上
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49．Try to give a program to evaluate the DTFT of the following finite-length sequence in the range  :

Then run the Program and compute the real and imaginary parts of the DTFT, and the magnitude and phase spectra. Is the DTFT a periodic function of w? If it is, what is the period? Can you explain the jumps in the phase spectrum?
function dtft(N);
y=1.25*ones(1,41);
t=-20:20;
w=-6*pi:12*pi/N:6*pi;
X=zeros(1,N+1);
for n=1:N+1;
    k=0;
    for j=1:41
        k=k+y(j)*exp(-i*w(n)*j);
    end
    X(n)=k;
end
figure(1);
subplot(2,1,1);stem(t,y);
subplot(2,1,2);plot(w,X);
figure(2);
subplot(2,1,1);plot(real(X));
subplot(2,1,2);plot(imag(X));
figure(3);
plot(unwrap(angle(X)));




059.Design a linear-phase FIR lowpass filter with the following specifications: passband edge at 2.2rad/sec, stopband edge at 4.1 rad/sec, maximum passband attenuation of 0.15dB, minimum stopband attenuation of 42dB, and a sampling frequency of 20rad/sec. Using the function fir1 and window of Kaiser to design. Show the impulse response coefficients and plot the gain response of the designed filter. Comment on your result.
fedge=[2.2/pi/2,4.1/pi/2];
mval=[1,0];
dev=[1-10^(-0.15/20),1-10^(-42/20)];
ft=20/2/pi;
[n,wn,beta,type]=kaiserord(fedge,mval,dev,ft);
b=fir1(n,wn,type,kaiser(n+1,beta),'noscale');
[h,w]=freqz(b,1,256);
plot(w/pi,20*log(abs(h)));
grid;
xlabel('\omega/\pi');ylabel('gain,db');


[ 此帖被阿董在2008-01-14 19:38重新编辑 ]

023.Design a Type 1 Chebyshev IIR lowpass filter meeting the specifications as below: sampling rate of 7kHz, passband edge frequency of 1.05kHz, stopband edge frequency of 1.4kHz, passband ripple of 0.4dB, and a minimum stopband attenuation of 50dB.Write down the exact expression for the transfer function generated. Does your design meet the specifications?
fs=7000;
wp=2*1050/7000;
ws=1.4*2/7;%归一
rp=0.4;
rs=50;
[n,wn]=cheb1ord(wp,ws,rp,rs);
[b,a]=cheby1(n,rp,wn,'low');
[h,w]=freqz(b,a,256);
plot(w/pi,20*log(abs(h)));
grid;
xlabel('\omega/\pi');ylabel('gain,db');

5．Write a MATLAB program to compute and plot the impulse response of a causal finite-dimensional discrete-time system characterized by a difference equation of the following form:

Generate and plot the first 41 samples of the impulse response of the system.

N=41;
x=[1 zeros(1,N-1)];
num=[1 -0.4 0.75];
den=[2.2403 2.4908 2.2403];
y=filter(num,den,x)
figure(1)
n=1:N;
stem(n,y)



026.Design a Type 2 Chebyshev IIR lowpass filter meeting the specifications as below: sampling rate of 3500Hz, passband edge frequency of 600Hz, stopband edge frequency of 1050Hz, passband ripple of 1dB, and a minimum stopband attenuation of 50dB.Write down the exact expression for the transfer function generated. Does your design meet the specifications?

>>Wp = 600/1750; Ws =1050/1750;
Rp = 1; Rs = 50;
[n,Wn] = cheb2ord(Wp,Ws,Rp,Rs)
n =

    5


Wn =

    0.6000

>> [b,a] = cheby2(n,Rs,Wn);
freqz(b,a,512,3500);
title('n=5 Chebyshev Type II Lowpass Filter')

029.Design an elliptic lowpass IIR filter meeting the specifications as below: sampling rate of 40kHz, passband edge frequency of 4kHz, stopband edge frequency of 8kHz, passband ripple of 0.5dB, and a minimum stopband attenuation of 40dB.Write down the exact expression for the transfer function generated. Does your design meet the specifications?
wp=4*2/40;
ws=8*2/40;
rp=0.5;
rs=40;
[n,wn]=ellipord(wp,ws,rp,rs,'s');
[b a]=ellip(n,rp,rs,wn,'low');
freqz(b,a)

29. Writing a MATLAB program to compute the linear convolution of two length-N sequences. Using this program to determine the following pair of sequences:
 

And plot the result sequence.
n=0:10;
g=exp(i*0.1*pi*n);
h=cos(0.3*pi*n);
y=conv(x,h);
plot(y);



010.Design a Type 2 Chebyshev IIR lowpass filter meeting the specifications as below: sampling rate 80kHz, passband edge frequency 4 kHz, the maximum passband ripple 0.5 dB, stopband egde frequency 6 kHz the minimum stopband attenuation 20dB,plot frequency-magnitude and check if your design fits the specification.
wp=2*4/80;
ws=6*2/80;
rp=0.5;
rs=20;
[n,wn]=cheb2ord(wp,ws,rp,rs);
[b,a]=cheby2(n,rs,wn,'low');
freqz(b,a);

11．Write a MATLAB program to compute and plot the response of input as  and a causal finite-dimensional discrete-time system characterized by a difference equation of the following form:

Generate and plot the first 41 samples of the sinusoidal response of the system.



b=[1 -2];
a=[1 0.1 -.06];
n=0:40;
x=cos(0.2*pi*n);
h=filter(b,a,x);
plot(n,h)

052.Design a Blackman FIR lowpass filter meeting the following specifications: passband edge frequency=2kHz, stopband edge frequency=2.3kHz, passband ripple δp=0.002, stopband rippleδs=0.002 and sampling rate of 20kHz. Plot its gain and phase responses and check if it meets the specifications?
rp=-20*log(1-0.002);
rs=rp;
wp=2*pi*2/20;
ws=2*pi*2.3/20;
detaw=ws-wp;
m=5.56*pi/detaw;
n=ceil(2*m);
f=[0 wp/2/pi ws/2/pi 1];
mag=[1 1 0 0];
b=firls(n,f,mag);
freqz(b);
pause
wo=wp/2/pi;
dp=0.002;
ds=0.002;
c=fircls1(n,wo,dp,ds);
freqz(c);

056.Design a linear-phase FIR lowpass filter with the following specifications: passband edge at 3.1rad/sec, stopband edge at 5 rad/sec, maximum passband attenuation of 0.2dB, minimum stopband attenuation of 45dB, and a sampling frequency of 40rad/sec. Using the function fir1 and window of Hamming to design. Show the impulse response coefficients and plot the gain response of the designed filter. Comment on your result.
wp=2*pi*3.1/40;
ws=2*pi*5/40;
w0=ws-wp;
m=3.32*pi/w0;
N=ceil(2*m);
b=hamming(N);
dp=1-10^(-0.2/20);
ds=10^(-45/20);
wo=0.31;
c=fircls1(N,wo,dp,ds);
freqz(c)

谢谢好人啊

045.Design a Hanning FIR lowpass filter meeting the following specifications: passband edge frequency=2kHz, stopband edge frequency=2.5kHz, passband ripple δp=0.005, stopband rippleδs=0.005, and sampling rate of 10kHz.Plot its gain and phase responses and check if it meets the specifications?

wp=2*pi*2/10;
ws=2*pi*2.5/10;
dp=0.005;
ds=0.005;
wo=(ws-ws)/pi;
n=ceil(2*3.11*pi/(ws-wp));
[b,a]= (fircls1(n,wo,dp,ds)
freqz(b,a);

20．Write a MATLAB program to compute and plot the response of input as  and a causal finite-dimensional discrete-time system characterized by a difference equation of the following form:

Generate and plot the first 41 samples of the response of the system.
b=[2.2403 2.4908 2.2403];
a=[1 -0.4 0.75];
n=0:15;
x=sin(2*pi*n)
y=filter(b,a,x);
t=0:40
N=41-length(y);
Y=[y,zeros(1,N)];
stem(t,Y)




01.Design an IIR butterworth digital lowpass filter with the following specifications: sampling rate 100kHz, passband edge frequency 25 kHz , the maximum passband ripple 0.5 dB, stopband egde frequency 34 kHz , stopband attenuation is 20dB,plot frequency-magnitude and check if your design fits the specification.
wp=2*25/100;
ws=2*34/100;
rp=0.5;rs=20;
[n,wn]=buttord(wp,ws,rp,rs);
[b a]=butter(n,wn,'low');
freqz(b,a)

为什么我们没有上机

Quote:

引用第9楼名柯于2008-01-14 19:44发表的  :
为什么我们没有上机

没上机多好啊.....

原来有这么多通信的兄弟啊

楼主好样的

谢谢楼主！

谢谢了！救命了！