仿真代码

close all;clear;clc;
fs=16000;fs_j=2000;f0=100;t=0:1/fs:10;
s_k = sin(2*pi*f0*t);
s_k_d = lowpass(s_k',1000,fs)';
s_k_j = resample(s_k_d',1,8)';
windowLen = 2^ceil(log2(fs));
windowLen1 = 2^ceil(log2(fs_j));
s1 = s_k(1,1:windowLen);
s2 = s_k_d(1,1:windowLen);
S1 = abs(fft(s1))*2/windowLen;
S2 = abs(fft(s2))*2/windowLen;
x_f = 0:fs/windowLen:fs;
x_f1 = 0:fs_j/windowLen1:fs_j;
windowLen1 = 2^ceil(log2(fs_j));
s3 = s_k_j(1,1:windowLen1);
S3 = abs(fft(s3))*2/windowLen1;
figure(1);
subplot(311);plot(x_f(1:windowLen/2),S1(1:windowLen/2));xlabel('频率');ylabel('功率');title('原始信号');
subplot(312);plot(x_f(1:windowLen/2),S2(1:windowLen/2));xlabel('频率');ylabel('功率');title('低通滤波信号');
subplot(313);plot(x_f1(1:windowLen1/2),S3(1:windowLen1/2));xlabel('频率');ylabel('功率');title('降采样信号');

仿真结果

仿真结论

• 当滤波降采样的信号是矩阵的时候，都是按列处理的。
• 由仿真结果可以看出，不管是滤波还是降采样，功率谱的幅值是几乎不变的。