6-31.m

MATLAB科学计算与工程分析源代码源程序5

clear
Fs = 1000;                    % 采样频率
T = 1/Fs;                     % 采样时间
L = 1000;                     % 信号长度
t = (0:L-1)*T;                % 时间向量
x = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t); 
y = x + 2*randn(size(t));     % 加噪声正弦信号
plot(Fs*t(1:50),y(1:50))
title('零平均值噪音信号');
xlabel('time (milliseconds)')
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2);
plot(f,2*abs(Y(1:NFFT/2))) 
title('y(t)单边振幅频谱')
xlabel('Frequency (Hz)')
ylabel('|Y(f)|')