巴特沃斯带通滤波器的命令是什么 [英] what is the command for butterworth bandpass filter

问题描述

我要使用频率为10-45s，45-150s和150-600s的带通滤波器进行滤波的信号数据.如何在Matlab中创建带通滤波器命令以对该频率进行滤波?

I have signal data to filter using bandpass filter which the frequencies are 10-45s, 45-150s and 150-600s. how to create bandpass filter command in matlab to filter that frequencies?

推荐答案

假定您具有信号处理工具箱(对于butter命令-如果butter不可用，请参见下面的代码)，并且您知道采样频率fs，您可以使用以下代码，使用低频和高频(以Hz为单位)-3dB的点来制作简单的递归巴特沃斯滤波器.较高的order s将为您提供更好的异频抑制性能，但需要更长的脉冲响应和更多的计算费用.

Assuming you have the signal processing toolbox (for the butter command - see lower code if butter is unavailable), and if you know the sampling frequency fs, you can make a simple recursive Butterworth filter using the low and high frequency (in Hz) -3dB poins using the following code. Higher orders will give you better off-frequency rejection at the expense of a longer impulse response and a little more computation expense.

[b,a] = butter(order, [lowFreq hiFreq]/(fs/2), 'bandpass');
 y = filter(b,a,x)

通过使用butter命令生成的系数对输入信号x进行滤波，即可获得输出信号y.

The output signal y is obtained by filtering the input signal x using the coefficients generated using the butter command.

如果要一次获得所有3个频段的输出，可以对3个单独的滤波器操作的输出求和，每个频段一个.但是，如果要保留频段之间的相位关系，则可能需要在filter上使用filtfilt命令.

If you want to have the output from all 3 bands at once, you can sum the outputs from 3 separate filter operations, one for each band. However, you may like to use the filtfilt command over filter when doing this if you want to preserve the phase relationship between the bands.

如果没有信号处理工具箱，则可以使用以下代码创建二阶带通巴特沃斯系数，其中dt = 1/fs和fl和fu分别是低截止频率和高截止频率.

If you do not have the signal processing toolbox, you cancreate 2nd order bandpass butterworth coefficients using the code below, where dt = 1/fs and fl and fu are low and high cutoff frequencies.

function [ b, a ] = butterTwoBp( dt, fl, fu ) 
q=pi*dt*(fu-fl);
r=pi*dt*(fu+fl);
N = (tan(q)^2) + sqrt(2)*tan(q) + 1;
M = (tan(q)^2) / N; %M after N because it depends on N
O = -cos(r) * (2*sqrt(2)*tan(q) + 4) / ((cos(q))*N);
P = (-2*(tan(q)^2) + ((  (2*cos(r))   /  (cos(q))   )^2) + 2 )  /   N;
Q = cos(r)*(2*sqrt(2)*tan(q) - 4)/(cos(q)*N);
R = (   (tan(q)^2) - sqrt(2)*tan(q) + 1   )  /  N;

b=[M 0 -2*M 0 M];
a=[1 O P Q R];

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