coding FM modulation

Question

Michael Adelman 2012-6-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41301-coding-fm-modulation

|hi,

I'm writing FM modulation according the plain math (without any matlab functions): http://www.st-andrews.ac.uk/~jcgl/Scots_Guide/RadCom/part12/page1.html

http://en.wikipedia.org/wiki/Frequency_modulation

Fs = 100e3; % Sampling frequency for audio
dt = 1/Fs;   %to reduce number of elements in the vector and increase 
  %             calaulation time.
T = 1;
%t = 0:dt:T/2;
t = (0:Fs-1)/Fs;
df = 1/T;
Fmax = 1/2/dt;
f = -Fmax:df:Fmax-1;
% Carrier
fc = 10e3;
% Information - Time domain
fm = 200;   %in Hz
Am = 1;
Kp = 7.5;    
ym = Am*sin(2*pi*fm.*t);
deltaF = Kp*Am;
% Modulation
beta = deltaF/(fm);
y = 4*cos(2*pi*fc.*t+beta*sin(2*pi*fm.*t));
% Frequency domain
Y = fftshift(fft(y))/length(y);  
% Plots - Time domain
figure(1);
subplot(211), plot(t,cos(2*pi*fm.*t)),axis([0.21 0.221 -1.5 1.5]), grid on;
subplot(212), plot(t,y), axis([0.21 0.221 -5 5]), grid on;
% Plots - frequency domain
figure(2);
plot(f,10*log10(abs(Y))), grid on;
%end code

Only at very high values of Kp I'm getting correct results in time domain but in frequency i'm still not getting correct results.

Please help.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Walter Roberson 2012-6-16

You are using *many* MATLAB functions. See http://www.mathworks.com/matlabcentral/answers/38787-what-can-be-programmed-without-any-built-in-functions

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Michael Adelman 2012-6-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41301-coding-fm-modulation#answer_50927

Hello Walter,

Thank you for the comment. I actually asked more on the FM modulation coding and incorrect outputs that get. Can you comment on that matter?

Thanks,

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Walter Roberson 2012-6-17

It is not possible to get an output without using a MATLAB function, so getting any output at all is incorrect when you are under the restriction of not using any MATLAB functions.

请先登录，再进行评论。