我正在MATLAB中进行信号过滤。我用3种不同的频率写了一个信号:
Fs = 8000; %// Sampling frequency
T = 1/Fs; %// Sample time
L = 16000; %// Length of signal
t = (0:L-1)*T; %// Time vector
y = 40*sin(2*pi*50*t) + 500*sin(2*pi*51*t) + 500*sin(2*pi*49*t);
现在我想使用汉宁窗口通过带通窗口滤波提取50Hz信号。
以下是设计过滤器的代码:
function Hd = HannFilter1
Fs = 8000; %// Sampling Frequency
N = 4096; %// Order
Fc1 = 49.5; %// First Cutoff Frequency
Fc2 = 50.5; %// Second Cutoff Frequency
flag = 'scale'; %// Sampling Flag
win = hann(N+1);
b = fir1(N, [Fc1 Fc2]/(Fs/2), 'bandpass', win, flag);
Hd = dfilt.dffir(b);
之后,我使用filter
进行过滤,如下所示:
yfilter = filter(Hd.Numerator,1,y);
NFFT = 2^nextpow2(L);
Y = fft(yfilter,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
figure;
subplot(2,1,1);
plot(yfilter);
subplot(2,1,2);
plot(f,2*abs(Y(1:NFFT/2+1)))
50Hz信号的最佳采样率是多少?而且非常重要的问题!在现实世界中,如平衡系统,主信号约为20Hz,环境噪声太大,我的解决方案过滤不能给出正确的答案。在这种情况下,我如何使用或选择最佳的过滤算法?
如果我的采样率为8000Hz 且我仅缓冲20000个样本,如何设计窄带通滤波器?
答案 0 :(得分:0)
因此,我通过降低采样率并通过此代码增加样本数据来解决问题:(正如Matt所述)
Fs = 1000; % Sampling frequency
T = 1/Fs; % Sample time
L = 60000; % Length of signal
t = (0:L-1)*T; % Time vector
for j=1:20
r1 = 5 + (1000-5).*rand(1,1);
r2 = 5 + (1000-5).*rand(1,1);
y = 10*sin(2*pi*14.8*t) + r1*sin(2*pi*14.2*t) + r2*sin(2*pi*15.5*t) + 1.1*rand(size(t));
yfilter = filter(Hd.Numerator,1,y);
max(yfilter(40000:50000))
end
我的过滤器是KAISER(FIR Badpass过滤器):
Fs = 1000; % Sampling Frequency
Fstop1 = 14.2; % First Stopband Frequency
Fpass1 = 14.6; % First Passband Frequency
Fpass2 = 15; % Second Passband Frequency
Fstop2 = 15.2; % Second Stopband Frequency
Dstop1 = 1e-06; % First Stopband Attenuation
Dpass = 0.057501127785; % Passband Ripple
Dstop2 = 1e-06; % Second Stopband Attenuation
flag = 'scale'; % Sampling Flag
% Calculate the order from the parameters using KAISERORD.
[N,Wn,BETA,TYPE] = kaiserord([Fstop1 Fpass1 Fpass2 Fstop2]/(Fs/2), [0 ...
1 0], [Dstop1 Dpass Dstop2]);
% Calculate the coefficients using the FIR1 function.
b = fir1(N, Wn, TYPE, kaiser(N+1, BETA), flag);
Hd = dfilt.dffir(b);
和20次迭代的滤波器幅度和随机噪声信号是:
max(yfilter(40000:50000))
10.01
10.02
10.01
10.00
10.01
10.03
10.01
10.02
....
但有一些问题:
1-我的样本数据长度是60000字节,另一方面是1000Hz的采样率,我等了60秒收集数据,那太久了!!! 当我将样本数据长度减少到大约3000个样本时,由于滤波器系数的数量约为4097,滤波结果非常糟糕。 当长度为3000个样本且我的滤波器系数大约为4097字节时,如何对信号进行滤波?当我减小滤波器的系数时,滤波后的信号结果是如此嘈杂。
2- 15 Hz信号的最佳采样率是多少?
感谢。