(代码)基于MATLAB的AM调制解调系统仿真报告 - 百度文库 ر

3.4ɽ

ɽնṩͶͬƵͬĸƵزcos(?ct)Խźţپ

ͨ˲ȡƵָԭźšʵ£

%---------------------------------------------------------------- % ؽز

s_carr =cos(2*pi*fc*t)

% ͬ

s_dem=s_am.*s_carr

% lfft

Lfft=length(t)%ȡʱijȲֵLfft

Lfft=2^ceil(log2(Lfft)+1)%LfftתΪżLfft ceil%ķȡ

% ƽźƵ

S_dem=fftshift(fft(s_dem,Lfft)/(length(t)));

% ɵͨ˲

h=fir1(60,[B_m*ts])%Ƶͨ˲ƵӦ˲60,Ƶ75Hz

% ͨ˲

s_rec=filter(h,1,s_dem)%ͨ˲filter˳s_demеĸƵûָźs_rec

% ƻָźƵ

S_rec=fftshift(fft(s_rec,Lfft)/(length(t)))

4

4.1źŲκƵ

21.510.5m(t)0-0.5-1-1.5-2-0.025-0.02-0.015-0.01-0.00500.005t(sec)0.010.0150.020.025

ͼ4źʱ

ͼ4ʾڵƵķźʱΡͼкֱӦʾʱźŷֵͼпԿźΪDzźš

0.50.450.40.350.3M(f)0.250.20.150.10.050-150-100-500f(Hz)50100150

ͼ5 źŵƵ

ͼ5ʾDzźŶӦƵסͼкʾƵʣʾƵ׷ֵͼпԿźƵҪڵƵΣźŴխԼ150Hz

4.2زźŲκƵ

1.510.5( t) scarr0-0.5-1-1.5-5-4-3-2-10t(sec)1234x 105-3

ͼ6 زźʱ

ͼ6ʾ˷Ͷ˵ƻźʹõزΡͼкʾزʱ䣬ʾزȡͼп֪εʹõزǷΪ1Ϊ2.0?10sƵΪ500Hz

-3