Problem : Vector length is different and fail to show the result of spectrum frequency.

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ong jia eek 2019-10-1

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/482961-problem-vector-length-is-different-and-fail-to-show-the-result-of-spectrum-frequency

Below is my code for spectrum frequency

It seems that i couldn't display the spectrum frequency code and I have no Idea why

fc=input('Enter the carrier signal freq in hz,fc=');

fm=input('Enter the modulating signal freq in hz,fm =');

m=input('Modulation index,m= ');

tm=(1/fm)*2;

t=0:1/(fc*1000):tm;

c=cos(2*pi*fc*t);%carrier signal

M=sin(2*pi*fm*t);% modulating signal

subplot(3,1,1);plot(t,c);

ylabel('amplitude');xlabel('time index');title('Carrier signal');

subplot(3,1,2);plot(t,M);

ylabel('amplitude');xlabel('time index');title('Modulating signal');

y=cos(2*pi*fc*t-(m.*cos(2*pi*fm*t)));

subplot(3,1,3);plot(t,y);

ylabel('amplitude');xlabel('time index');title('Frequency Modulated signal');

F = 1000; % sampling frequency

f0 = fc; % carrier

f1 = fm; % modulating tone

beta = m; % modulation index

% signal, spectrum

N = 1000;

t = (0:N-1)*(1/F); % delt = 1us

z = fftshift(fft(y))/N;

f = (-N/2:N/2-1)*(F/N);

% predicted sidebands for the positive frequencies only

n = 4;

sidamp = (1/2)*besselj(0:n,beta);

sidamp = [fliplr(sidamp(2:end)), sidamp];

sidf = (f0-n*f1):f1:(f0+n*f1);

figure(2)

subplot(2, 1, 1);

plot(f,abs(z))

xlim([-2*f0 2*f0])

subplot(2, 1 ,2 );plot(f,abs(z),sidf,sidamp,'o')

xlim([f0-f1*10 f0+f1*10]) % sidebands at the pos frequencies

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